[ { "text": "Implications of Planck2015 for inflationary, ekpyrotic and anamorphic\n bouncing cosmologies: The results from Planck2015, when combined with earlier observations from\nWMAP, ACT, SPT and other experiments, were the first observations to disfavor\nthe \"classic\" inflationary paradigm. To satisfy the observational constraints,\ninflationary theorists have been forced to consider plateau-like inflaton\npotentials that introduce more parameters and more fine-tuning, problematic\ninitial conditions, multiverse-unpredictability issues, and a new 'unlikeliness\nproblem.' Some propose turning instead to a \"postmodern\" inflationary paradigm\nin which the cosmological properties in our observable universe are only\nlocally valid and set randomly, with completely different properties (and\nperhaps even different physical laws) existing in most regions outside our\nhorizon. By contrast, the new results are consistent with the simplest versions\nof ekpyrotic cyclic models in which the universe is smoothed and flattened\nduring a period of slow contraction followed by a bounce, and another promising\nbouncing theory, anamorphic cosmology, has been proposed that can produce\ndistinctive predictions.", "category": "astro-ph_CO" }, { "text": "The spectacular cluster chain Abell 781 as observed with LOFAR, GMRT,\n and XMM-Newton: A number of merging galaxy clusters show the presence of large-scale radio\nemission associated with the intra-cluster medium (ICM). These synchrotron\nsources are generally classified as radio haloes and radio relics. Whilst it is\ncommonly accepted that mergers play a crucial role in the formation of radio\nhaloes and relics, not all the merging clusters show the presence of giant\ndiffuse radio sources and this provides important information concerning\ncurrent models. The Abell 781 complex is a spectacular system composed of an\napparent chain of clusters on the sky. Its main component is undergoing a\nmerger and hosts peripheral emission that is classified as a candidate radio\nrelic and a disputed radio halo. We used new LOw Frequency ARay (LOFAR)\nobservations at 143 MHz and archival Giant Metrewave Radio Telescope (GMRT)\nobservations at 325 and 610 MHz to study radio emission from non-thermal\ncomponents in the ICM of Abell 781. Complementary information came from\nXMM-Newton data, which allowed us to investigate the connection with the\nthermal emission and its complex morphology. The origin of the peripheral\nemission is still uncertain. We speculate that it is related to the interaction\nbetween a head tail radio galaxy and shock. However, the current data allow us\nonly to set an upper limit of $\\mathcal{M} < 1.4$ on the Mach number of this\nputative shock. Instead, we successfully characterise the surface brightness\nand temperature jumps of a shock and two cold fronts in the main cluster\ncomponent of Abell 781. Their positions suggest that the merger is involving\nthree substructures. We do not find any evidence for a radio halo either at the\ncentre of this system or in the other clusters of the chain. We place an upper\nlimit to the diffuse radio emission in the main cluster of Abell 781 that is a\nfactor of 2 below the current radio power-mass relation for giant radio haloes.", "category": "astro-ph_CO" }, { "text": "Sound velocity effects on the phase transition gravitational wave\n spectrum in the sound shell model: A cosmological first-order phase transition gravitational wave could provide\na novel approach to studying the early Universe. In most cases, the acoustic\ngravitational wave from the sound wave mechanism is dominant. Considering\ndifferent sound velocities in symmetric and broken phases, we study sound\nvelocity effects on the acoustic phase transition gravitational wave spectra in\nthe sound shell model. We demonstrate that different sound velocities could\nobviously modify the peak frequency and peak amplitude of the gravitational\nwave power spectra. Therefore, taking more realistic sound velocities might\nprovide more accurate predictions for various gravitational wave experiments.", "category": "astro-ph_CO" }, { "text": "Spinning primordial black holes formed during a matter-dominated era: We study the formation of spinning primordial black holes during an early\nmatter-dominated era. Using non-linear 3+1D general relativistic simulations,\nwe compute the efficiency of mass and angular momentum transfer in the process\n-- which we find to be $\\mathcal{O}(10\\%)$ and $\\mathcal{O}(5\\%)$,\nrespectively. We show that subsequent evolution is important due to the seed\nPBH accreting non-rotating matter from the background, which decreases the\ndimensionless spin. Unless the matter era is short, we argue that the final\ndimensionless spin will be negligible.", "category": "astro-ph_CO" }, { "text": "Detectability of Gravitational Waves from High-Redshift Binaries: Recent non-detection of gravitational-wave backgrounds from pulsar timing\narrays casts further uncertainty on the evolution of supermassive black hole\nbinaries. We study the capabilities of current gravitational-wave observatories\nto detect individual binaries and demonstrate that, contrary to conventional\nwisdom, some are in principle detectable throughout the Universe. In\nparticular, a binary with rest-frame mass $\\gtrsim10^{10}\\,M_\\odot$ can be\ndetected by current timing arrays at arbitrarily high redshifts. The same claim\nwill apply for less massive binaries with more sensitive future arrays. As a\nconsequence, future searches for nanohertz gravitational waves could be\nexpanded to target evolving high-redshift binaries. We calculate the maximum\ndistance at which binaries can be observed with pulsar timing arrays and other\ndetectors, properly accounting for redshift and using realistic binary\nwaveforms.", "category": "astro-ph_CO" }, { "text": "Thermal Fluctuations of Dark Matter in Bouncing Cosmology: We investigate the statistical nature of the dark matter particles produced\nin bouncing cosmology, especially, the evolution of its thermal fluctuations.\nBy explicitly deriving and solving the equation of motion of super-horizon\nmode, we fully determine the evolution of thermal perturbation of dark matter\nin a generic bouncing background. And we also show that the evolution of\nsuper-horizon modes is stable and will not ruin the background evolution of a\ngeneric bouncing universe till the Planck scale. Given no super-horizon thermal\nperturbation of dark matter appears in standard inflation scenario such as\nWIMP(-less) miracles, such super-horizon thermal perturbation of dark matter\ngenerated during the generic bouncing universe scenario may be significant for\ntesting and distinguishing these two scenario in near future.", "category": "astro-ph_CO" }, { "text": "Precision growth index using the clustering of cosmic structures and\n growth data: We use the clustering properties of Luminous Red Galaxies (LRGs) and the\ngrowth rate data provided by the various galaxy surveys in order to constrain\nthe growth index ($\\gamma$) of the linear matter fluctuations. We perform a\nstandard $\\chi^2$-minimization procedure between theoretical expectations and\ndata, followed by a joint likelihood analysis and we find a value of\n$\\gamma=0.56\\pm 0.05$, perfectly consistent with the expectations of the\n$\\Lambda$CDM model, and $\\Omega_{m0} =0.29\\pm 0.01$, in very good agreement\nwith the latest Planck results. Our analysis provides significantly more\nstringent growth index constraints with respect to previous studies, as\nindicated by the fact that the corresponding uncertainty is only $\\sim 0.09\n\\gamma$. Finally, allowing $\\gamma$ to vary with redshift in two manners\n(Taylor expansion around $z=0$, and Taylor expansion around the scale factor),\nwe find that the combined statistical analysis between our clustering and\nliterature growth data alleviates the degeneracy and obtain more stringent\nconstraints with respect to other recent studies.", "category": "astro-ph_CO" }, { "text": "The Atlas3D project - XV. Benchmark for early-type galaxies scaling\n relations from 260 dynamical models: mass-to-light ratio, dark matter,\n Fundamental Plane and Mass Plane: We study the volume-limited and nearly mass selected (stellar mass M>6*10^9\nMsun) Atlas3D sample of 260 early-type galaxies. We construct detailed\naxisymmetric dynamical models (JAM), which allow for orbital anisotropy,\ninclude a dark matter halo, and reproduce in detail both the galaxy images and\nthe high-quality integral-field stellar kinematics. We derive accurate total\nM/L and dark matter fractions f_DM, within a sphere of radius r=Re. We also\nmeasure the stellar M/L and derive a median dark matter fraction f_DM=13%. We\nfind that the thin two-dimensional subset spanned by galaxies in the\n(M_JAM,sigma_e,R_e) coordinates system, which we call the Mass Plane (MP) has\nan observed rms scatter of 19% and an intrinsic one of 11%. The MP satisfies\nthe scalar virial relation M_JAM sigma_e^2 R_e within our tight errors.\nHowever, the details of how both Re and sigma_e are determined are critical in\ndefining the precise deviation from the virial exponents. We revisit the\n(M/L)-sigma_e relation, which describes most of the deviations between the MP\nand the FP. The best-fitting relation is (M/L) sigma_e^0.72 (r-band). It\nprovides an upper limit to any systematic increase of the IMF mass\nnormalization with sigma_e. We study of the link between sigma_e and the\ngalaxies circular velocity V_circ within 1Re (where stars dominate) and find\nthe relation max(V_circ)~1.76*sigma_e, which has an observed scatter of 7%. The\naccurate parameters described in this paper are used in the companion Paper XX\nof this series to explore the variation of global galaxy properties, including\nthe IMF, on the projections of the MP. [Abridged]", "category": "astro-ph_CO" }, { "text": "Dark energy, integrated Sachs-Wolfe effect and large-scale magnetic\n fields: The impact of large-scale magnetic fields on the interplay between the\nordinary and integrated Sachs-Wolfe effects is investigated in the presence of\na fluctuating dark energy component. The modified initial conditions of the\nEinstein-Boltzmann hierarchy allow for the simultaneous inclusion of dark\nenergy perturbations and of large-scale magnetic fields. The temperature and\npolarization angular power spectra are compared with the results obtained in\nthe magnetized version of the (minimal) concordance model. Purported\ncompensation effects arising at large scales are specifically investigated. The\nfluctuating dark energy component modifies, in a computable manner, the shapes\nof the 1- and 2-$\\sigma$ contours in the parameter space of the magnetized\nbackground. The allowed spectral indices and magnetic field intensities turn\nout to be slightly larger than those determined in the framework of the\nmagnetized concordance model where the dark energy fluctuations are absent.", "category": "astro-ph_CO" }, { "text": "Exacerbating the cosmological constant problem with interacting dark\n energy: Future cosmological surveys will probe the expansion history of the universe\nand constrain phenomenological models of dark energy. Such models do not\naddress the fine-tuning problem of the vacuum energy, i.e. the cosmological\nconstant problem (c.c.p.), but can make it spectacularly worse. We show that\nthis is the case for 'interacting dark energy' models in which the masses of\nthe dark matter states depend on the dark energy sector. If realised in nature,\nthese models have far-reaching implications for proposed solutions to the\nc.c.p. that require the number of vacua to exceed the fine-tuning of the vacuum\nenergy density. We show that current estimates of the number of flux vacua in\nstring theory, $N_{\\rm vac} \\sim {\\cal O}(10^{272,000})$, is far too small to\nrealise certain simple models of interacting dark energy \\emph{and} solve the\ncosmological constant problem anthropically. These models admit distinctive\nobservational signatures that can be targeted by future gamma-ray\nobservatories, hence making it possible to observationally rule out the\nanthropic solution to the cosmological constant problem in theories with a\nfinite number of vacua.", "category": "astro-ph_CO" }, { "text": "Galaxy Zoo and ALFALFA: Atomic Gas and the Regulation of Star Formation\n in Barred Disc Galaxies: We study the observed correlation between atomic gas content and the\nlikelihood of hosting a large scale bar in a sample of 2090 disc galaxies. Such\na test has never been done before on this scale. We use data on morphologies\nfrom the Galaxy Zoo project and information on the galaxies' HI content from\nthe ALFALFA blind HI survey. Our main result is that the bar fraction is\nsignificantly lower among gas rich disc galaxies than gas poor ones. This is\nnot explained by known trends for more massive (stellar) and redder disc\ngalaxies to host more bars and have lower gas fractions: we still see at fixed\nstellar mass a residual correlation between gas content and bar fraction. We\ndiscuss three possible causal explanations: (1) bars in disc galaxies cause\natomic gas to be used up more quickly, (2) increasing the atomic gas content in\na disc galaxy inhibits bar formation, and (3) bar fraction and gas content are\nboth driven by correlation with environmental effects (e.g. tidal triggering of\nbars, combined with strangulation removing gas). All three explanations are\nconsistent with the observed correlations. In addition our observations suggest\nbars may reduce or halt star formation in the outer parts of discs by holding\nback the infall of external gas beyond bar co-rotation, reddening the global\ncolours of barred disc galaxies. This suggests that secular evolution driven by\nthe exchange of angular momentum between stars in the bar, and gas in the disc,\nacts as a feedback mechanism to regulate star formation in intermediate mass\ndisc galaxies.", "category": "astro-ph_CO" }, { "text": "[FeII] as a tracer supernova rate: Supernovae play an integral role in the feedback of processed material into\nthe ISMof galaxies and are responsible for most of the chemical enrichment of\nthe universe. The rate of supernovae can also reveal the star formation\nhistories. Supernova rate is usually measured through the non-thermal radio\ncontinuum luminosity, but in this paper we establish a quantitative\nrelationship between the [FeII]1.26 luminosity and supernova rate in a sample\nof 11 near-by starburst galaxies. SINFONI data cubes are used to perform a\npixel pixel analysis of this correlation. Using Br equivalent width and\nluminosity as the only observational inputs into Starburst 99, the supernova\nrate is derived at each pixel and a map of supernova rate is created. This is\nthen compared morphologically and quantitatively to [FeII]1.26 luminosity map.\nWe find a strong linear and morphological correlation between supernova rate\nand [FeII]1.26 on a pixel-pixel basis: log SNrate yr-1 pc-2 = (1.01 \\pm 0.2)\n\\ast log[FeII]1.26 ergs-1 pc-2 - 41.17 \\pm 0.9 The Starburst 99 derived\nsupernova rates are also in good agreement with the radio derived supernova\nrates, which further demonstrates the strength of [FeII] as a tracer of\nsupernova rate. With the strong correlation found in this sample of galaxies,\nwe now qualitatively use [FeII]1.26 to derive supernova rate on either a\npixel-pixel or integrated galactic basis.", "category": "astro-ph_CO" }, { "text": "Haro15: Is it actually a low metallicity galaxy?: We present a detailed study of the physical properties of the nebular\nmaterial in multiple knots of the blue compact dwarf galaxy Haro 15. Using long\nslit and echelle spectroscopy, obtained at Las Campanas Observatory, we study\nthe physical conditions (electron density and temperature), ionic and total\nchemical abundances of several atoms, reddening and ionization structure. The\nlatter was derived by comparing the oxygen and sulphur ionic ratios to their\ncorresponding observed emission line ratios (the eta and eta' plots) in\ndifferent regions of the galaxy. Applying direct and empirical methods for\nabundance determination, we perform a comparative analysis between these\nregions.", "category": "astro-ph_CO" }, { "text": "Constraints on primordial black holes and curvature perturbations from\n the global 21cm signal: The recent observations of the global 21cm signal by EDGES and gravitational\nwaves by LIGO/VIGO have revived interest in PBHs. Different from previous\nworks, we investigate the influence of PBHs on the evolution of the IGM for the\nmass range $6\\times 10^{13} {\\rm g} \\lesssim M_{\\rm PBH}\\lesssim 3\\times\n10^{14} \\rm g$. Since the lifetime of these PBHs is smaller than the present\nage of the Universe, they have evaporated by the present day. Due to Hawking\nradiation, the heating effects of PBHs on the IGM can suppress the absorption\namplitude of the global 21cm signal. In this work, by requiring that the\ndifferential brightness temperature of the global 21cm signals in the redshift\nrange of $10\\lesssim z \\lesssim 30$, e.g., $\\delta T_{b} \\lesssim -100~\\rm mK$,\nwe obtain upper limits on the initial mass fraction of PBHs. We find that the\nstrongest upper limit is $\\beta_{\\rm PBH} \\sim 2\\times 10^{-30}$. Since the\nformation of PBHs is related to primordial curvature perturbations, by using\nthe constraints on the initial mass fraction of PBHs we obtain the upper limits\non the power spectrum of primordial curvature perturbations for the scale range\n$8.0\\times 10^{15}\\lesssim k \\lesssim 1.8\\times 10^{16}~\\rm Mpc^{-1}$,\ncorresponding to the mass range considered here. We find that the strongest\nupper limit is $\\mathcal P_{\\mathcal R}(k) \\sim 0.0046$. By comparing with\nprevious works, we find that for the mass range (or the scale range)\ninvestigated in this work the global 21cm signals or the 21cm power spectrum\nshould give the strongest upper limits on the initial mass fraction of PBHs and\non the power spectrum of primordial curvature perturbations.", "category": "astro-ph_CO" }, { "text": "Constraining the Black Hole Mass Spectrum with LISA Observations II:\n Direct comparison of detailed models: A number of scenarios have been proposed for the origin of the supermassive\nblack holes (SMBHs) that are found in the centres of most galaxies. Many such\nscenarios predict a high-redshift population of massive black holes (MBHs),\nwith masses in the range 100 to 100000 times that of the Sun. When the Laser\nInterferometer Space Antenna (LISA) is finally operational, it is likely that\nit will detect on the order of 100 of these MBH binaries as they merge. The\ndifferences between proposed population models produce appreciable effects in\nthe portion of the population which is detectable by LISA, so it is likely that\nthe LISA observations will allow us to place constraints on them. However,\ngravitational wave detectors such as LISA will not be able to detect all such\nmergers nor assign precise black hole parameters to the merger, due to weak\ngravitational wave signal strengths. This paper explores LISA's ability to\ndistinguish between several MBH population models. In this way, we go beyond\npredicting a LISA observed population and consider the extent to which LISA\nobservations could inform astrophysical modellers. The errors in LISA parameter\nestimation are applied with a direct method which generates random sample\nparameters for each source in a population realisation. We consider how the\ndistinguishability varies depending on the choice of source parameters (1 or 2\nparameters chosen from masses, redshift or spins) used to characterise the\nmodel distributions, with confidence levels determined by 1 and 2-dimensional\ntests based on the Kolmogorov-Smirnov test.", "category": "astro-ph_CO" }, { "text": "Detecting Baryon Acoustic Oscillations in Dark Matter from Kinematic\n Weak Lensing Surveys: We investigate the feasibility of extracting Baryon Acoustic Oscillations\n(BAO) from cosmic shear tomography. We particularly focus on the BAO scale\nprecision that can be achieved by future spectroscopy-based, kinematic weak\nlensing (KWL) surveys \\citep[e.g.,][]{Huff13} in comparison to the traditional\nphotometry-based weak lensing surveys. We simulate cosmic shear tomography data\nof such surveys with a few simple assumptions to focus on the BAO information,\nextract the spacial power spectrum, and constrain the recovered BAO feature.\nDue to the small shape noise and the shape of the lensing kernel, we find that\na Dark Energy Task Force Stage IV version of such KWL survey can detect the BAO\nfeature in dark matter by $3$-$\\sigma$ and measure the BAO scale at the\nprecision level of 4\\% while it will be difficult to detect the feature in\nphotometry-based weak lensing surveys. With a more optimistic assumption, a\nKWL-Stage IV could achieve a $\\sim 2\\%$ BAO scale measurement with\n$4.9$-$\\sigma$ confidence. A built-in spectroscopic galaxy survey within such\nKWL survey will allow cross-correlation between galaxies and cosmic shear,\nwhich will tighten the constraint beyond the lower limit we present in this\npaper and therefore possibly allow a detection of the BAO scale bias between\ngalaxies and dark matter.", "category": "astro-ph_CO" }, { "text": "Revisiting Primordial Black Holes Constraints from Ionization History: Much attention has been drawn to the recent discoveries by the Advanced Laser\nInterferometer Gravitational-Wave Observatory (LIGO) of merging intermediate\nmass black holes. Of particular interest is the possibility that the merger\nevents detected could be evidence of dark matter in the form of primordial\nblack holes (PBHs). It has been argued that the presence of many black holes\nwould effect the thermal and ionization history of the universe via their\naccretion of matter which would have strong signatures in the Cosmic Microwave\nBackground's (CMB) power spectra evident in the damping of anisotropies and\nchange in low-$l$ polarization power. In general the accretion is quite\nsensitive to the specific physics involved and the conditions of the early\nuniverse. In this work, we take a minimal approach and find constraints on PBHs\nnot including the model dependent effects of nonlinear structure of formation\nor transition between different accretion models which would work to increase\nthe effect. In addition, we include the relative velocity between dark matter\nand baryonic matter including the effects of supersonic streaming at high\nredshift which work to significantly reduce the constraining power. We also\nexamine the constraints on more astrophysically-motivated extended black hole\nmass functions and discuss how mergers might effect this distribution. We find\nconstraints on PBHs in the range $ \\approx 30 M_\\odot$, finding that they could\nnot compose more than $10\\%$ of the total dark matter content.", "category": "astro-ph_CO" }, { "text": "Energy-conservation constraints on cosmic string loop production and\n distribution functions: A network of cosmic strings would lead to gravitational waves which may be\ndetected by pulsar timing or future interferometers. The details of the\ngravitational wave signal depend on the distribution of cosmic string loops,\nwhich are produced by intercommutations from the scaling network of long\nstrings. We analyze the limits imposed by energy conservation, i.e., by the\nfact that the total amount of string flowing into loops cannot exceed the\namount leaving the long strings. We show that some recent suggestions for the\ncosmic string loop production rate and distribution are ruled out by these\nlimits. As a result, gravitational waves based on such suggestions, in\nparticular \"model 3\" used in LIGO data analysis, are not to be expected.", "category": "astro-ph_CO" }, { "text": "Observations of flat-spectrum radio sources at 850 microns from the\n James Clerk Maxwell Telescope II. April 2000 to June 2005: Calibrated data for 143 flat-spectrum extragalactic radio sources are\npresented at a wavelength of 850 microns covering a five-year period from April\n2000. The data, obtained at the James Clerk Maxwell Telescope using the SCUBA\ncamera in pointing mode, were analysed using an automated pipeline process\nbased on the Observatory Reduction and Acquisition Control - Data Reduction\n(ORAC-DR) system. This paper describes the techniques used to analyse and\ncalibrate the data, and presents the database of results along with a\nrepresentative sample of the better-sampled lightcurves. A re-analysis of\npreviously published data from 1997 to 2000 is also presented. The combined\ncatalogue, comprising 10493 flux density measurements, provides a unique and\nvaluable resource for studies of extragalactic radio sources.", "category": "astro-ph_CO" }, { "text": "The accretion of dark matter subhaloes within the cosmic web: primordial\n anisotropic distribution and its universality: The distribution of galaxies displays anisotropy on different scales and it\nis often referred as galaxy alignment. To understand the origin of galaxy\nalignments on small scales, one must investigate how galaxies were accreted in\nthe early universe and quantify their primordial anisotropic at the time of\naccretion. In this paper we use N-body simulations to investigate the accretion\nof dark matter subhaloes, focusing on their alignment with the host halo shape\nand the orientation of mass distribution on large scale, defined using the\nhessian matrix of the density field. The large/small (e1/e3) eigenvalues of the\nhessian matrix define the fast/slow collapse direction of dark matter on large\nscale. We find that: 1) the halo major axis is well aligned with the e3 (slow\ncollapse) direction, and it is stronger for massive haloes; 2) subhaloes are\npredominately accreted along the major axis of the host halo, and the alignment\nincreases with the host halo mass. Most importantly, this alignment is\nuniversal; 3) accretion of subhaloes with respect to the e3 direction is not\nuniversal. In massive haloes, subhaloes are accreted along the e3 (even\nstronger than the alignment with the halo major axis), but in low-mass haloes\nsubhaloes are accreted perpendicular to the e3. The transit mass is lower at\nhigh redshift. The last result well explains the puzzled correlation (both in\nrecent observations and simulations) that massive galaxies/haloes have their\nspin perpendicular to the filament, and the spin of low-mass galaxies/haloes is\nslightly aligned with the filament, under the assumption that the orbital\nangular momentum of subhaloes is converted to halo spin.", "category": "astro-ph_CO" }, { "text": "Non-parametric Lagrangian biasing from the insights of neural nets: We present a Lagrangian model of galaxy clustering bias in which we train a\nneural net using the local properties of the smoothed initial density field to\npredict the late-time mass-weighted halo field. By fitting the mass-weighted\nhalo field in the AbacusSummit simulations at z=0.5, we find that including\nthree coarsely spaced smoothing scales gives the best recovery of the halo\npower spectrum. Adding more smoothing scales may lead to 2-5% underestimation\nof the large-scale power and can cause the neural net to overfit. We find that\nthe fitted halo-to-mass ratio can be well described by two directions in the\noriginal high-dimension feature space. Projecting the original features into\nthese two principal components and re-training the neural net either reproduces\nthe original training result, or outperforms it with a better match of the halo\npower spectrum. The elements of the principal components are unlikely to be\nassigned physical meanings, partly owing to the features being highly\ncorrelated between different smoothing scales. Our work illustrates a potential\nneed to include multiple smoothing scales when studying galaxy bias, and this\ncan be done easily with machine-learning methods that can take in high\ndimensional input feature space.", "category": "astro-ph_CO" }, { "text": "On the Sunyaev-Zel'dovich effect from dark matter annihilation or decay\n in galaxy clusters: We revisit the prospects for detecting the Sunyaev Zel'dovich (SZ) effect\ninduced by dark matter (DM) annihilation or decay. We show that with standard\n(or even extreme) assumptions for DM properties, the optical depth associated\nwith relativistic electrons injected from DM annihilation or decay is much\nsmaller than that associated with thermal electrons, when averaged over the\nangular resolution of current and future experiments. For example, we find:\n$\\tau_{\\rm DM} \\sim 10^{-9}-10^{-5}$ (depending on the assumptions) for $\\mchi\n= 1$ GeV and a density profile $\\rho\\propto r^{-1}$ for a template cluster\nlocated at 50 Mpc and observed within an angular resolution of $10\"$, compared\nto $\\tau_{\\rm th}\\sim 10^{-3}-10^{-2}$. This, together with a full spectral\nanalysis, enables us to demonstrate that, for a template cluster with generic\nproperties, the SZ effect due to DM annihilation or decay is far below the\nsensitivity of the Planck satellite. This is at variance with previous claims\nregarding heavier annihilating DM particles. Should DM be made of lighter\nparticles, the current constraints from 511 keV observations on the\nannihilation cross section or decay rate still prevent a detectable SZ effect.\nFinally, we show that spatial diffusion sets a core of a few kpc in the\nelectron distribution, even for very cuspy DM profiles, such that improving the\nangular resolution of the instrument, e.g. with ALMA, does not necessarily\nimprove the detection potential. We provide useful analytical formulae\nparameterized in terms of the DM mass, decay rate or annihilation cross section\nand DM halo features, that allow quick estimates of the SZ effect induced by\nany given candidate and any DM halo profile.", "category": "astro-ph_CO" }, { "text": "Multi-scale initial conditions for cosmological simulations: We discuss a new algorithm to generate multi-scale initial conditions with\nmultiple levels of refinements for cosmological \"zoom-in\" simulations. The\nmethod uses an adaptive convolution of Gaussian white noise with a real space\ntransfer function kernel together with an adaptive multi-grid Poisson solver to\ngenerate displacements and velocities following first (1LPT) or second order\nLagrangian perturbation theory (2LPT). The new algorithm achieves RMS relative\nerrors of order 10^(-4) for displacements and velocities in the refinement\nregion and thus improves in terms of errors by about two orders of magnitude\nover previous approaches. In addition, errors are localized at coarse-fine\nboundaries and do not suffer from Fourier-space induced interference ringing.\nAn optional hybrid multi-grid and Fast Fourier Transform (FFT) based scheme is\nintroduced which has identical Fourier space behaviour as traditional\napproaches. Using a suite of re-simulations of a galaxy cluster halo our real\nspace based approach is found to reproduce correlation functions, density\nprofiles, key halo properties and subhalo abundances with per cent level\naccuracy. Finally, we generalize our approach for two-component baryon and\ndark-matter simulations and demonstrate that the power spectrum evolution is in\nexcellent agreement with linear perturbation theory. For initial baryon density\nfields, it is suggested to use the local Lagrangian approximation in order to\ngenerate a density field for mesh based codes that is consistent with\nLagrangian perturbation theory instead of the current practice of using the\nEulerian linearly scaled densities.", "category": "astro-ph_CO" }, { "text": "Primordial non-Gaussianity and Bispectrum Measurements in the Cosmic\n Microwave Background and Large-Scale Structure: The most direct probe of non-Gaussian initial conditions has come from\nbispectrum measurements of temperature fluctuations in the Cosmic Microwave\nBackground and of the matter and galaxy distribution at large scales. Such\nbispectrum estimators are expected to continue to provide the best constraints\non the non-Gaussian parameters in future observations. We review and compare\nthe theoretical and observational problems, current results and future\nprospects for the detection of a non-vanishing primordial component in the\nbispectrum of the Cosmic Microwave Background and large-scale structure, and\nthe relation to specific predictions from different inflationary models.", "category": "astro-ph_CO" }, { "text": "Galaxy-galaxy weak gravitational lensing in $f(R)$ gravity: We present an analysis of galaxy-galaxy weak gravitational lensing (GGL) in\nchameleon $f(R)$ gravity - a leading candidate of non-standard gravity models.\nFor the analysis we have created mock galaxy catalogues based on dark matter\nhaloes from two sets of numerical simulations, using a halo occupation\ndistribution (HOD) prescription which allows a redshift dependence of galaxy\nnumber density. To make a fairer comparison between the $f(R)$ and $\\Lambda$CDM\nmodels, their HOD parameters are tuned so that the galaxy two-point correlation\nfunctions in real space (and therefore the projected two-point correlation\nfunctions) match. While the $f(R)$ model predicts an enhancement of the\nconvergence power spectrum by up to $\\sim30\\%$ compared to the standard\n$\\Lambda$CDM model with the same parameters, the maximum enhancement of GGL is\nonly half as large and less than 5\\% on separations above $\\sim1$-$2h^{-1}$Mpc,\nbecause the latter is a cross correlation of shear (or matter, which is more\nstrongly affected by modified gravity) and galaxy (which is weakly affected\ngiven the good match between galaxy auto correlations in the two models)\nfields. We also study the possibility of reconstructing the matter power\nspectrum by combination of GGL and galaxy clustering in $f(R)$ gravity. We find\nthat the galaxy-matter cross correlation coefficient remains at unity down to\n$\\sim2$-$3h^{-1}$Mpc at relevant redshifts even in $f(R)$ gravity, indicating\njoint analysis of GGL and galaxy clustering can be a powerful probe of matter\ndensity fluctuations in chameleon gravity. The scale dependence of the model\ndifferences in their predictions of GGL can potentially allow to break the\ndegeneracy between $f(R)$ gravity and other cosmological parameters such as\n$\\Omega_m$ and $\\sigma_8$.", "category": "astro-ph_CO" }, { "text": "Evolution of gaseous disk viscosity driven by supernova explosion in\n star-forming galaxies at high redshift: Motivated by Genzel et al.'s observations of high-redshift star-forming\ngalaxies, containing clumpy and turbulent rings or disks, we build a set of\nequations describing the dynamical evolution of gaseous disks with inclusion of\nstar formation and its feedback. Transport of angular momentum is due to\n\"turbulent\" viscosity induced by supernova explosions in the star formation\nregion. Analytical solutions of the equations are found for the initial cases\nof a gaseous ring and the integrated form for a gaseous disk, respectively. For\na ring with enough low viscosity, it evolves in a slow processes of gaseous\ndiffusion and star formation near the initial radius. For a high viscosity, the\nring rapidly diffuses in the early phase. The diffusion drives the ring into a\nregion with a low viscosity and start the second phase undergoing pile-up of\ngas at a radius following the decreased viscosity torque. The third is a\nsharply deceasing phase because of star formation consumption of gas and\nefficient transportation of gas inward forming a stellar disk. We apply the\nmodel to two $z\\sim 2$ galaxies BX 482 and BzK 6004, and find that they are\nundergoing a decline in their star formation activity.", "category": "astro-ph_CO" }, { "text": "Extensions to models of the galaxy-halo connection: We explore two widely used empirical models for the galaxy-halo connection,\nsubhalo abundance matching (SHAM) and the halo occupation distribution (HOD)\nand compare their predictions with the hydrodynamical simulation IllustrisTNG\n(TNG) for a range of statistics that quantify the galaxy distribution at\n$n_{\\rm gal}\\approx1.3\\times10^{-3}\\,[{\\rm Mpc}/h]^{-3}$. We observe that in\ntheir most straightforward implementations, both models fail to reproduce the\ntwo-point clustering measured in TNG. We find that SHAM models constructed\nusing the relaxation velocity, $V_{\\rm relax}$, and the peak velocity, $V_{\\rm\npeak}$, perform best, and match the clustering reasonably well, although\nneither model captures adequately the one-halo clustering. Splitting the total\nsample into sub-populations, we discover that SHAM overpredicts the clustering\nof high-mass, blue, star-forming, and late-forming galaxies and uderpredicts\nthat of low-mass, red, quiescent, and early-forming galaxies. We also study\nvarious baryonic effects, finding that subhalos in the dark-mater-only\nsimulation have consistently higher values of their SHAM-proxy properties than\ntheir full-physics counterparts. We then consider a two-dimensional\nimplementation of the HOD model augmented with a secondary parameter\n(environment, velocity anisotropy, $\\sigma^2R_{\\rm halfmass}$, and total\npotential) and tuned so as to match the two-point clustering of the\nIllustrisTNG galaxies on large scales. We analyze these galaxy populations\nadopting alternative statistical tools such as galaxy-galaxy lensing,\nvoid-galaxy cross-correlations and cumulants of the smoothed density field,\nfinding that the hydrodynamical galaxy distribution disfavors $\\sigma^2 R_{\\rm\nhalfmass}$ and the total potential as secondary parameters, while the\nenvironment and velocity anisotropy samples are consistent with full-physics\nacross all statistical probes examined.", "category": "astro-ph_CO" }, { "text": "GRB Probes of the Early Universe with EXIST: With the Swift detection of GRB090423 at z = 8.2, it was confirmed that GRBs\nare now detectable at (significantly) larger redshifts than AGN, and so can\nindeed be used as probes of the Early Universe. The proposed Energetic X-ray\nImaging Survey Telescope (EXIST) mission has been designed to detect and\npromptly measure redshifts and both soft X-ray (0.1 - 10 keV) and simultaneous\nnUV-nIR (0.3 - 2.3microns) imaging and spectra for GRBs out to redshifts z ~18,\nwhich encompasses (or even exceeds) current estimates for Pop III stars that\nare expected to be massive and possibly GRB sources. Scaling from Swift for the\n~10X greater sensitivity of EXIST, more than 100 GRBs at z >=8 may be detected\nand would provide direct constraints on the formation and evolution of the\nfirst stars and galaxies. For GRBs at redshifts z >= 8, with Lyman breaks at\ngreater than 1.12microns, spectra at resolution R = 30 or R = 3000 for\nafterglows with AB magnitudes brighter than 24 or 20 (respectively) within\n~3000sec of trigger will directly probe the Epoch of Reionization, formation of\ngalaxies, and cosmic star formation rate. The proposed EXIST mission can probe\nthese questions, and many others, given its unparalleled combination of\nsensitivity and spatial-spectral-temporal coverage and resolution. Here we\nprovide an overview of the key science objectives for GRBs as probes of the\nearly Universe and of extreme physics, and the mission plan and technical\nreadiness to bring this to EXIST.", "category": "astro-ph_CO" }, { "text": "Imprint of Scalar Dark Energy on Cosmic Microwave Background\n Polarization: We study the imprint of a coupling of scalar dark energy to photon on the\ncosmic microwave background (CMB) polarization. The time-evolving field value\nas well as the perturbation of the scalar generically induce $B$-mode\npolarization. Future CMB data will find either a cosmic parity violation in\ntemperature-polarization correlation due to the field value, or\nperturbation-induced $B$-mode polarization that is almost indistinguishable\nfrom that generated by gravitational lensing or primordial gravitational waves.", "category": "astro-ph_CO" }, { "text": "The Herschel Virgo Cluster Survey: I. Luminosity functions: We describe the Herschel Virgo Cluster Survey (HeViCS) and the first data\nobtained as part of the Science Demonstration Phase (SDP). The data cover a\ncentral 4x4 sq deg region of the cluster. We use SPIRE and PACS photometry data\nto produce 100, 160, 250, 350 and 500 micron luminosity functions (LFs) for\noptically bright galaxies that are selected at 500 micron and detected in all\nbands. We compare these LFs with those previously derived using IRAS, BLAST and\nHerschel-ATLAS data. The Virgo Cluster LFs do not have the large numbers of\nfaint galaxies or examples of very luminous galaxies seen previously in surveys\ncovering less dense environments.", "category": "astro-ph_CO" }, { "text": "Simulations of primary beam effects on the cosmic bispectrum phase\n observed with the Hydrogen Epoch of Reionization Array: The 21~cm transition from neutral Hydrogen promises to be the best\nobservational probe of the Epoch of Reionisation. The main difficulty in\nmeasuring the 21 cm signal is the presence of bright foregrounds that require\nvery accurate interferometric calibration. Closure quantities may circumvent\nthe calibration requirements but may be, however, affected by direction\ndependent effects, particularly antenna primary beam responses. This work\ninvestigates the impact of antenna primary beams affected by mutual coupling on\nthe closure phase and its power spectrum. Our simulations show that primary\nbeams affected by mutual coupling lead to a leakage of foreground power into\nthe EoR window, which can be up to $\\sim4$ orders magnitude higher than the\ncase where no mutual coupling is considered. This leakage is, however,\nessentially confined at $k < 0.3$~$h$~Mpc$^{-1}$ for triads that include 29~m\nbaselines. The leakage magnitude is more pronounced when bright foregrounds\nappear in the antenna sidelobes, as expected. Finally, we find that triads that\ninclude mutual coupling beams different from each other have power spectra\nsimilar to triads that include the same type of mutual coupling beam,\nindicating that beam-to-beam variation within triads (or visibility pairs) is\nnot the major source of foreground leakage in the EoR window.", "category": "astro-ph_CO" }, { "text": "The Clowes-Campusano Large Quasar Group Survey: I. GALEX selected sample\n of LBGs at z$\\sim$1: The nature of galaxy structures on large scales is a key observational\nprediction for current models of galaxy formation. The SDSS and 2dF galaxy\nsurveys have revealed a number of structures on 40-150 h^-1 Mpc scales at low\nredshifts, and some even larger ones. To constrain galaxy number densities,\nluminosities, and stellar populations in large structures at higher redshift,\nwe have investigated two sheet-like structures of galaxies at z=0.8 and 1.3\nspanning 150 h^-1 comoving Mpc embedded in large quasar groups extending over\nat least 200 h^-1 Mpc. We present first results of an analysis of these\nsheet--like structures using two contiguous 1deg GALEX fields (FUV and NUV)\ncross-correlated with optical data from the Sloan Digital Sky Survey (SDSS). We\nderive a sample of 462 Lyman Break Galaxy (LBG) candidates coincident with the\nsheets. Using the GALEX and SDSS data, we show that the overall average\nspectral energy distribution of a LBG galaxy at z~1 is flat (in f_lambda) in\nthe rest frame wavelength range from 1500A, to 4000A, implying evolved\npopulations of stars in the LBGs. From the luminosity functions we get\nindications for overdensities in the two LQGs compared to their foreground\nregions. Similar conclusions come from the calculation of the 2-point\ncorrelation function, showing a 2sigma overdensity for the LBGs in the z~0.8\nLQG on scales of 1.6 to 4.8 Mpc, indicating similar correlation scales for our\nLBG sample as their z~3 counterparts.", "category": "astro-ph_CO" }, { "text": "The (relative) size does not matter in inflation: We show that a tiny correction to the inflaton potential can make critical\nchanges in the inflationary observables for some types of inflation models.", "category": "astro-ph_CO" }, { "text": "Constraining Dark-Matter Ensembles with Supernova Data: The constraints on non-minimal dark sectors involving ensembles of unstable\ndark-matter species are well established and quite stringent in cases in which\nthese species decay to visible-sector particles. However, in cases in which\nthese ensembles decay exclusively to other, lighter dark-sector states, the\ncorresponding constraints are less well established. In this paper, we\ninvestigate how information about the expansion rate of the universe at low\nredshifts gleaned from observations of Type Ia supernovae can be used to\nconstrain ensembles of unstable particles which decay primarily into dark\nradiation.", "category": "astro-ph_CO" }, { "text": "The chemical evolution of IC10: Dwarf irregular galaxies are relatively simple unevolved objects where it is\neasy to test models of galactic chemical evolution. We attempt to determine the\nstar formation and gas accretion history of IC10, a local dwarf irregular for\nwhich abundance, gas, and mass determinations are available. We apply detailed\nchemical evolution models to predict the evolution of several chemical elements\n(He, O, N, S) and compared our predictions with the observational data. We\nconsider additional constraints such as the present-time gas fraction, the star\nformation rate (SFR), and the total estimated mass of IC10. We assume a dark\nmatter halo for this galaxy and study the development of a galactic wind. We\nconsider different star formation regimes: bursting and continuous. We explore\ndifferent wind situations: i) normal wind, where all the gas is lost at the\nsame rate and ii) metal-enhanced wind, where metals produced by supernovae are\npreferentially lost. We study a case without wind. We vary the star formation\nefficiency (SFE), the wind efficiency, and the time scale of the gas infall,\nwhich are the most important parameters in our models. We find that only models\nwith metal-enhanced galactic winds can reproduce the properties of IC10. The\nstar formation must have proceeded in bursts rather than continuously and the\nbursts must have been less numerous than ~10 over the whole galactic lifetime.\nFinally, IC10 must have formed by a slow process of gas accretion with a\ntimescale of the order of 8 Gyr.", "category": "astro-ph_CO" }, { "text": "The formation of CDM haloes I: Collapse thresholds and the ellipsoidal\n collapse model: In the excursion set approach to structure formation initially spherical\nregions of the linear density field collapse to form haloes of mass $M$ at\nredshift $z_{\\rm id}$ if their linearly extrapolated density contrast, averaged\non that scale, exceeds some critical threshold, $\\delta_{\\rm c}(z_{\\rm id})$.\nThe value of $\\delta_{\\rm c}(z_{\\rm id})$ is often calculated from the\nspherical or ellipsoidal collapse model, which provide well-defined predictions\ngiven auxiliary properties of the tidal field at a given location. We use two\ncosmological simulations of structure growth in a $\\Lambda$ cold dark matter\nscenario to quantify $\\delta_{\\rm c}(z_{\\rm id})$, its dependence on the\nsurrounding tidal field, as well as on the shapes of the Lagrangian regions\nthat collapse to form haloes at $z_{\\rm id}$. Our results indicate that the\nellipsoidal collapse model provides an accurate description of the mean\ndependence of $\\delta_{\\rm c}(z_{\\rm id})$ on both the strength of the tidal\nfield and on halo mass. However, for a given $z_{\\rm id}$, $\\delta_{\\rm\nc}(z_{\\rm id})$ depends strongly on the halo's characteristic formation\nredshift: the earlier a halo forms, the higher its initial density contrast.\nSurprisingly, the majority of haloes forming $today$ fall below the ellipsoidal\ncollapse barrier, contradicting the model predictions. We trace the origin of\nthis effect to the non-spherical shapes of Lagrangian haloes, which arise\nnaturally due to the asymmetry of the linear tidal field. We show that a\nmodified collapse model, that accounts for the triaxial shape of protohaloes,\nprovides a more accurate description of the measured minimum overdensities of\nrecently collapsed objects.", "category": "astro-ph_CO" }, { "text": "Circular Polarization of the Astrophysical Gravitational Wave Background: The circular polarization of gravitational waves is a powerful observable to\ntest parity violation in gravity and to distinguish between the primordial or\nthe astrophysical origin of the stochastic background. This property comes from\nthe expected unpolarized nature of the homogeneous and isotropic astrophysical\nbackground, contrary to some specific cosmological sources that can produce a\npolarized background. However, in this work we show that there is a\nnon-negligible amount of circular polarization also in the astrophysical\nbackground, generated by Poisson fluctuations in the number of unresolved\nsources, which can be detected by the third-generation interferometers with\nsignal-to-noise ratio larger than one. We also explain in which cases the\ngravitational wave maps can be cleaned from this extra source of noise,\nexploiting the frequency and the angular dependence, in order to search for\nsignals from the early Universe. Future studies about the detection of\npolarized cosmological backgrounds with ground- and space-based interferometers\nshould account for the presence of such a foreground contribution.", "category": "astro-ph_CO" }, { "text": "Going beyond the Kaiser redshift-space distortion formula: a full\n general relativistic account of the effects and their detectability in galaxy\n clustering: Kaiser redshift-space distortion formula describes well the clustering of\ngalaxies in redshift surveys on small scales, but there are numerous additional\nterms that arise on large scales. Some of these terms can be described using\nNewtonian dynamics and have been discussed in the literature, while the others\nrequire proper general relativistic description that was only recently\ndeveloped. Accounting for these terms in galaxy clustering is the first step\ntoward tests of general relativity on horizon scales. The effects can be\nclassified as two terms that represent the velocity and the gravitational\npotential contributions. Their amplitude is determined by effects such as the\nvolume and luminosity distance fluctuation effects and the time evolution of\ngalaxy number density and Hubble parameter. We compare the Newtonian\napproximation often used in the redshift-space distortion literature to the\nfully general relativistic equation, and show that Newtonian approximation\naccounts for most of the terms contributing to velocity effect. We perform a\nFisher matrix analysis of detectability of these terms and show that in a\nsingle tracer survey they are completely undetectable. To detect these terms\none must resort to the recently developed methods to reduce sampling variance\nand shot noise. We show that in an all-sky galaxy redshift survey at low\nredshift the velocity term can be measured at a few sigma if one can utilize\nhalos of mass M>10^12 Msun (this can increase to 10-sigma or more in some more\noptimistic scenarios), while the gravitational potential term itself can only\nbe marginally detected. We also demonstrate that the general relativistic\neffect is not degenerate with the primordial non-Gaussian signature in galaxy\nbias, and the ability to detect primordial non-Gaussianity is little\ncompromised.", "category": "astro-ph_CO" }, { "text": "Mass-radius relation of Newtonian self-gravitating Bose-Einstein\n condensates with short-range interactions: II. Numerical results: We develop the suggestion that dark matter could be a Bose-Einstein\ncondensate. We determine the mass-radius relation of a Newtonian\nself-gravitating Bose-Einstein condensate with short-range interactions\ndescribed by the Gross-Pitaevskii-Poisson system. We numerically solve the\nequation of hydrostatic equilibrium describing the balance between the\ngravitational attraction and the pressure due to quantum effects (Heisenberg's\nuncertainty principle) and short-range interactions (scattering). We connect\nthe non-interacting limit to the Thomas-Fermi limit. We also consider the case\nof attractive self-interaction. We compare the exact mass-radius relation\nobtained numerically with the approximate analytical relation obtained with a\nGaussian ansatz. An overall good agreement is found.", "category": "astro-ph_CO" }, { "text": "Extended Light in E/S0 Galaxies and Implications for Disk Rebirth: The recent discovery of extended ultraviolet (XUV) disks around a large\nfraction of late-type galaxies provides evidence for unexpectedly large-scale\ndisk building at recent epochs. Combining GALEX UV observations with deep\noptical and Spitzer IR imaging, we search for XUV disks in a sample of nearby\nlow-to-intermediate mass E/S0 galaxies to explore evidence for disk rebuilding\nafter mergers. Preliminary visual classification yields ten XUV-disk candidates\nfrom the full sample of 30, intriguingly similar to the ~30% frequency for\nlate-type galaxies. These XUV candidates occur at a wide range of masses and on\nboth the red and blue sequences in color vs. stellar mass, indicating a\npossible association with processes like gas accretion and/or galaxy\ninteractions that would affect the galaxy population broadly. We go on to apply\nthe quantitative Type 1 and Type 2 XUV-disk definitions to a nine-galaxy\nsubsample analyzed in detail. For this subsample, six of the nine are Type 1\nXUVs, i.e., galaxies with UV structure beyond the expected star formation\nthreshold. The other three come close to satisfying the Type 2 definition, but\nthat definition proves problematic to apply to this sample: the NUV-derived\nstar formation threshold radii for our E/S0s often lie inside the 80% Ks-band\nlight (K80) radii, violating an implicit assumption of the Type 2 definition,\nor lie outside but not as far as the definition requires. Nonetheless, the\nthree otherwise Type 2-like galaxies (\"modified Type 2 XUVs\") have higher star\nformation rates and bluer FUV - NUV colors than the Type 1 XUVs in the sample.\nWe propose that Type 1 XUVs may reflect early or inefficient stages of star\nformation, while modified Type 2 XUVs perhaps reflect inside-out disk regrowth.", "category": "astro-ph_CO" }, { "text": "The ATLAS Survey of the CDFS and ELAIS-S1 Fields: The first phase of the ATLAS (Australia Telescope Large Area Survey) project\nsurveyed a total 7 square degrees down to 30 micro Jy rms at 1.4 GHz and is the\nlargest sensitive radio survey ever attempted. We report on the scientific\nachievements of ATLAS to date and plans to extend the project as a path finder\nfor the proposed EMU (Evolutionary map of the Universe) project which has been\ndesigned to use ASKAP (Australian Square Kilometre Array Pathfinder).", "category": "astro-ph_CO" }, { "text": "Constraints on parity violation from ACTpol and forecasts for\n forthcoming CMB experiments: We use the ACTpol published cosmic microwave background (CMB) polarization\ndata to constrain cosmological birefringence, a tracer of parity violation\nbeyond the standard model of particle physics. To this purpose, we employ all\nthe polarized ACTpol spectra, including the cross-correlations between\ntemperature anisotropy and B mode polarization (TB) and between E mode and B\nmode (EB), which are most sensitive to the effect. We build specific, so-called\nD-estimators for birefringence and assess their performances and error budgets\nby using realistic Monte Carlo simulations based on the experimental\ncharacteristics provided by the ACTpol collaboration. We determine the optimal\nmultipole range for our analysis to be $250 < \\ell < 3025$ over which we find a\nnull result for the uniform birefringence angle $\\alpha = 0.29^\\circ \\pm\n0.28^\\circ$ (stat.) $\\pm 0.5^\\circ$ (syst.), the latter uncertainty being the\nestimate published by the ACTpol team on their global systematic error budget.\nWe show that this result holds consistently when other multipole ranges are\nconsidered. Finally, we forecast the capability of several forthcoming ground\nbased, balloon and space borne CMB experiments to constrain the birefringence\nangle, showing, e.g., that the proposed post-Planck COrE satellite mission\ncould in principle constrain $\\alpha$ at a level of 10 arcsec, provided that\nall systematics are under control. Under the same circumstances, we find the\nCOrE constraints to be at least 2 or 3 times better than what could ideally be\nachieved by the other experiments considered.", "category": "astro-ph_CO" }, { "text": "Cosmological evidence for leptonic asymmetry after Planck: Recently, the Planck satellite found a larger and most precise value of the\nmatter energy density, that impacts on the present values of other cosmological\nparameters such as the Hubble constant, the present cluster abundances and the\nage of the Universe. The existing tension between Planck determination of these\nparameters in the frame of the base LambdaCDM model and their direct\nmeasurements generated lively discussions and several interpretations. In this\npaper we quantify this tension by exploring several extensions of the base\nLambdaCDM model that include the leptonic asymmetry. We set bounds on the\nradiation content of the Universe and neutrino properties by using the latest\ncosmological measurements, imposing also self-consistent BBN constraints on the\nprimordial helium abundance. For all cosmological asymmetric models we find the\npreference of cosmological data for smaller values of active and sterile\nneutrino masses. This increases the tension between cosmological and short\nbaseline neutrino oscillation data that favor a sterile neutrino with the mass\nof around 1 eV. For the case of degenerate massive neutrinos, we find that the\ndiscrepancies with direct determinations of the Hubble constant, the present\ncluster abundances and the age of the Universe are alleviated at ~ 1.3 sigma\nfor all leptonic asymmetric models. We also find ~2 sigma statistical evidence\nof the preference of cosmological data for the normal neutrino hierarchy. This\nis more evident for the case of cosmological models involving leptonic\nasymmetry and three massive neutrino species. We conclude that the current\ncosmological data favor the leptonic asymmetric extension of the base LambdaCDM\nmodel and normal neutrino mass hierarchy over the models with additional\nsterile neutrino species and/or inverted neutrino mass hierarchy.", "category": "astro-ph_CO" }, { "text": "Intergalactic stellar populations in intermediate redshift clusters: A substantial fraction of the total stellar mass in rich clusters of galaxies\nresides in a diffuse intergalactic component usually referred to as the\nIntra-Cluster Light (ICL). Theoretical models indicate that these intergalactic\nstars originate mostly from the tidal interaction of the cluster galaxies\nduring the assembly history of the cluster, and that a significant fraction of\nthese stars could have formed in-situ from the late infall of cold metal-poor\ngas clouds onto the cluster. The models make predictions about the age\ndistribution of the ICL stars, which may provide additional observational\nconstraints. However, these models also over-predict the fraction of stellar\nmass in the ICL by a substantial margin. Here we present population synthesis\nmodels for the ICL of a dumb-bell dominated intermediate redshift (z=0.29)\nX-ray cluster for which we have deep MOS data obtained with the FORS2\ninstrument. In a previous paper we have proposed that the dumbell galaxy act as\na grinding machine tearing to pieces the galaxies that pass nearby thus\nenriching the intergalactic medium. In this paper we analyze the spectra at\ndifferent locations within the ICL and find that it is dominated by old metal\nrich stars, at odds with what has been found in nearby clusters where the stars\nthat dominate the ICL are old and metal poor. While we see a weak evidence of a\nyoung, metal poor, component, if real, these young stars would amount to less\nthan 1% of the total ICL mass, much less than the up to 30% predicted by the\nmodels. We propose that the very metal rich (i.e. 2.5 times solar) stars in the\nICL of our cluster, which comprise approximately 40% of the total mass,\noriginate mostly from the central dumb-bell galaxy, while the remaining solar\nand metal poor stars come from spiral, post-starburst (E+A), and metal poor\ndwarf galaxies. About 16% of the ICL stars are old and metal poor.", "category": "astro-ph_CO" }, { "text": "The evolution of the star forming sequence in hierarchical galaxy\n formation models: It has been argued that the specific star formation rates of star forming\ngalaxies inferred from observational data decline more rapidly below z = 2 than\nis predicted by hierarchical galaxy formation models. We present a detailed\nanalysis of this problem by comparing predictions from the GALFORM\nsemi-analytic model with an extensive compilation of data on the average star\nformation rates of star-forming galaxies. We also use this data to infer the\nform of the stellar mass assembly histories of star forming galaxies. Our\nanalysis reveals that the currently available data favour a scenario where the\nstellar mass assembly histories of star forming galaxies rise at early times\nand then fall towards the present day. In contrast, our model predicts stellar\nmass assembly histories that are almost flat below z = 2 for star forming\ngalaxies, such that the predicted star formation rates can be offset with\nrespect to the observational data by factors of up to 2-3. This disagreement\ncan be explained by the level of coevolution between stellar and halo mass\nassembly that exists in contemporary galaxy formation models. In turn, this\narises because the standard implementations of star formation and supernova\nfeedback used in the models result in the efficiencies of these process\nremaining approximately constant over the lifetime of a given star forming\ngalaxy. We demonstrate how a modification to the timescale for gas ejected by\nfeedback to be reincorporated into galaxy haloes can help to reconcile the\nmodel predictions with the data.", "category": "astro-ph_CO" }, { "text": "Probing primordial features with the primary CMB: CMB photons travel from the last scattering surface, when the primary CMB has\nbeen generated, along the surface of the light cone to us. During their travel,\nthey are affected by many secondary effects such as the integrated Sachs-Wolfe\neffect and CMB lensing. These CMB secondary effects modify the CMB primary\npower spectrum adding degeneracies and decreasing the sensibility to primordial\nparameters. The possibility to reconstruct the primary CMB anisotropies will\nallow us to have a more direct observable to test the physics of the early\nuniverse. We propose to study the imprint of features in the primordial power\nspectrum with the primary CMB after the subtraction of the reconstructed ISW\nsignal from the observed CMB temperature angular power spectrum. We consider\nthe application to features models able to fit two of the large scales\nanomalies observed in the CMB temperature angular power spectrum: the deficit\nof power at $\\ell \\sim 2$ and at $\\ell \\sim 22$. This method allows to improve\nsignificantly the constraints on the features parameters up to $16\\%$ for\nmodels predicting a suppression of power of the quadrupole and up to $27\\%$ for\nmodels with features at $\\ell \\sim 22$, assuming instrumental sensitivity\nsimilar to the $Planck$ satellite (depending on the goodness of the ISW\nreconstruction). Furthermore, it gives the opportunity to understand if these\nanomalies are attributed to early- or late-time physics.", "category": "astro-ph_CO" }, { "text": "Halo/Galaxy Bispectrum with Primordial non-Gaussianity from integrated\n Perturbation Theory (iPT): We derive a formula for the halo/galaxy bispectrum on the basis of the\nintegrated Perturbation Theory (iPT). In addition to the gravity-induced\nnon-Gaussianity, we consider the non-Gaussianity of the primordial curvature\nperturbations, and investigate in detail the effect of such primordial\nnon-Gaussianity on the large-scale halo/galaxy bispectrum. In iPT, the effects\nof primordial non-Gaussianity are wholly encapsulated in the linear\n(primordial) polyspectra, and we systematically calculate the contributions to\nthe large-scale behaviors arising from the three types of primordial bispectrum\n(local-, equilateral-, and orthogonal-types), and primordial trispectrum of the\nlocal-type non-Gaussianity. We find that the equilateral- and orthogonal-type\nnon-Gaussianities show distinct scale-dependent behaviors which can dominate\nthe gravity-induced non-Gaussianity at very large scales. For the local-type\nnon-Gaussianity, higher-order loop corrections are found to give a\nsignificantly large contribution to the halo/galaxy bispectrum of the squeezed\nshape, and eventually dominate over the other contributions on large scales. A\ndiagrammatic approach based on the iPT helps us to systematically investigate\nan impact of such higher-order contributions to the large-scale halo/galaxy\nbispectrum.", "category": "astro-ph_CO" }, { "text": "Power Spectra beyond the Slow Roll Approximation in Theories with\n Non-Canonical Kinetic Terms: We derive analytical expressions for the power spectra at the end of\ninflation in theories with two inflaton fields and non-canonical kinetic terms.\nWe find that going beyond the slow-roll approximation is necessary and that the\nnature of the non-canonical terms have an important impact on the final power\nspectra at the end of inflation. We study five models numerically and find\nexcellent agreement with our analytical results. Our results emphasise the fact\nthat going beyond the slow-roll approximation is important in times of\nhigh-precision data coming from cosmological observations.", "category": "astro-ph_CO" }, { "text": "Herschel-ATLAS/GAMA: a census of dust in optically selected galaxies\n from stacking at submillimetre wavelengths: We use the Herschel-ATLAS survey to conduct the first large-scale statistical\nstudy of the submm properties of optically selected galaxies. Using ~80,000\nr-band selected galaxies from 126 deg^2 of the GAMA survey, we stack into submm\nimaging at 250, 350 and 500{\\mu}m to gain unprecedented statistics on the dust\nemission from galaxies at z < 0.35. We find that low redshift galaxies account\nfor 5% of the cosmic 250{\\mu}m background (4% at 350{\\mu}m; 3% at 500{\\mu}m),\nof which approximately 60% comes from 'blue' and 20% from 'red' galaxies\n(rest-frame g - r). We compare the dust properties of different galaxy\npopulations by dividing the sample into bins of optical luminosity, stellar\nmass, colour and redshift. In blue galaxies we find that dust temperature and\nluminosity correlate strongly with stellar mass at a fixed redshift, but red\ngalaxies do not follow these correlations and overall have lower luminosities\nand temperatures. We make reasonable assumptions to account for the\ncontaminating flux from lensing by red sequence galaxies and conclude that\ngalaxies with different optical colours have fundamentally different dust\nemission properties. Results indicate that while blue galaxies are more\nluminous than red galaxies due to higher temperatures, the dust masses of the\ntwo samples are relatively similar. Dust mass is shown to correlate with\nstellar mass, although the dust/stellar mass ratio is much higher for low\nstellar mass galaxies, consistent with the lowest mass galaxies having the\nhighest specific star formation rates. We stack the 250{\\mu}m/NUV luminosity\nratio, finding results consistent with greater obscuration of star formation at\nlower stellar mass and higher redshift. Submm luminosities and dust masses of\nall galaxies are shown to evolve strongly with redshift, indicating a fall in\nthe amount of obscured star formation in ordinary galaxies over the last four\nbillion years.", "category": "astro-ph_CO" }, { "text": "Constraints on the Redshift Evolution of the L_X-SFR Relation from the\n Cosmic X-Ray Backgrounds: Observations of local star forming galaxies have revealed a correlation\nbetween the rate at which galaxies form stars and their X-Ray luminosity. We\ncombine this correlation with the most recent observational constraints on the\nintegrated star formation rate density, and find that star forming galaxies\naccount for 5-20% of the total soft and hard X-ray backgrounds, where the\nprecise number depends on the energy band and the assumed average X-ray\nspectral energy distribution of the galaxies below ~20 keV. If we combine the\nL_X-SFR relation with recently derived star formation rate function, then we\nfind that star forming galaxies whose X-ray flux falls well (more than a factor\nof 10) below the detection thresholds of the Chandra Deep Fields, can fully\naccount for the unresolved soft X-ray background, which corresponds to ~6% of\nits total. Motivated by this result, we put limits on the allowed redshift\nevolution of the parameter c_X \\equiv L_X/SFR, and/or its evolution towards\nlower and higher star formation rates. If we parametrize the redshift evolution\nof c_X ~ (1+z)^b, then we find that b \\leq 1.3 (95% CL). On the other hand, the\nobserved X-ray luminosity functions (XLFs) of star forming galaxies indicate\nthat c_X may be increasing towards higher redshifts and/or higher star\nformation rates at levels that are consistent with the X-ray background, but\npossibly at odds with the locally observed L_X-SFR relation.", "category": "astro-ph_CO" }, { "text": "Gamma rays from ultracompact primordial dark matter minihalos: Ultracompact minihalos have recently been proposed as a new class of dark\nmatter structure. These minihalos would be produced by phase transitions in the\nearly Universe or features in the inflaton potential, and constitute\nnon-baryonic massive compact halo objects (MACHOs) today. We examine the\nprospect of detecting ultracompact minihalos in gamma-rays if dark matter\nconsists of self-annihilating particles. We compute present-day fluxes from\nminihalos produced in the electron-positron annihilation epoch, and the QCD and\nelectroweak phase transitions in the early Universe. Even at a distance of 100\npc, minihalos produced during the electron-positron annihilation epoch should\nbe eminently detectable today, either by the Fermi satellite, current Air\nCherenkov telescopes, or even in archival EGRET data. Within ~1 pc, minihalos\nformed in the QCD phase transition would have similar predicted fluxes to the\ndwarf spheroidal galaxies targeted by current indirect dark matter searches, so\nmight also be detectable by present or upcoming experiments.", "category": "astro-ph_CO" }, { "text": "Reconstruction of high-resolution SZ maps from heterogeneous datasets\n using needlets: The aim of this work is to propose a joint exploitation of heterogeneous\ndatasets from high-resolution/few-channel experiments and\nlow-resolution/many-channel experiments by using a multiscale needlet Internal\nLinear Combination (ILC), in order to optimize the thermal Sunyaev-Zeldovich\n(SZ) effect reconstruction at high resolution. We highlight that needlet ILC is\na powerful and tunable component separation method which can easily deal with\nmultiple experiments with various specifications. Such a multiscale analysis\nrenders possible the joint exploitation of high-resolution and low-resolution\ndata, by performing for each needlet scale a combination of some specific\nchannels, either from one dataset or both datasets, selected for their\nrelevance to the angular scale considered, thus allowing to simultaneously\nextract high resolution SZ signal from compact clusters and remove Galactic\nforeground contamination at large scales.", "category": "astro-ph_CO" }, { "text": "Star Formation in Nearby Isolated Galaxies: We use the FUV fluxes measured with the GALEX to study the star formation\nproperties of galaxies collected in the \"Local Orphan Galaxies\" catalog (LOG).\nAmong 517 LOG galaxies having radial velocities V(LG) < 3500 km/s and Galactic\nlatitudes |b|> 15 degr, 428 objects have been detected in FUV. We briefly\ndiscuss some scaling relations between the specific star formation rate (SSFR)\nand stellar mass, HI-mass, morphology, and surface brightness of galaxies\nsituated in extremely low density regions of the Local Supercluster. Our sample\nis populated with predominantly late-type, gas-rich objects with the median\nmorphological type of Sdm. Only 5% of LOG galaxies are classified as early\ntypes: E, S0, S0/a, however, they systematically differ from normal E and S0\ngalaxies by lower luminosity and presence of gas and dust. We find that almost\nall galaxies in our sample have their SSFR below 0.4 [Gyr^{-1}]. This limit is\nalso true even for a sample of 260 active star-burst Markarian galaxies\nsituated in the same volume. The existence of such a quasi-Eddington limit for\ngalaxies seems to be a key factor which characterizes the transformation of gas\ninto stars at the current epoch.", "category": "astro-ph_CO" }, { "text": "Supervoids in the WISE-2MASS catalogue imprinting Cold Spots in the\n Cosmic Microwave Background: The Cold Spot (CS) is a clear feature in the Cosmic Microwave Background\n(CMB); it could be of primordial origin, or caused by a intervening structure\nalong the line of sight. We identified a large projected underdensity in the\nrecently constructed WISE-2MASS all-sky infrared galaxy catalogue aligned with\nthe Cold Spot direction at $(l,b)\\approx(209^\\circ,-57^\\circ)$. It has an\nangular size of tens of degrees, and shows a $\\sim20\\%$ galaxy underdensity in\nthe center. Moreover, we find another large underdensity in the projected\nWISE-2MASS galaxy map at $(l,b)\\approx(101^\\circ,46^\\circ)$ (hereafter Draco\nSupervoid), also aligned with a CMB decrement, although less significant than\nthat of the CS direction. Motivated by these findings, we develop spherically\nsymmetric Lemaitre-Tolman-Bondi (LTB) compensated void models to explain the\nobserved CMB decrements with these two underdensities, or \"supervoids\". Within\nour perturbative treatment of the LTB voids, we find that the Integrated\nSachs-Wolfe and Riess-Sciama effects due to the Draco Supervoid can account for\nthe CMB decrement observed in the same direction. On the contrary, the\nextremely deep CMB decrement in the CS direction is more difficult to explain\nby the presence of the CS supervoid only. Nevertheless, the probability of a\nrandom alignment between the CS and the corresponding supervoid is disfavored,\nand thus its contribution as a secondary anisotropy cannot be neglected. We\ncomment on how the approximations used in this paper, in particular the\nassumption of spherical symmetry, could change quantitatively our conclusions\nand might provide a better explanation for the CMB CS.", "category": "astro-ph_CO" }, { "text": "Warm Dark Matter as a solution to the small scale crisis: new\n constraints from high redshift Lyman-alpha forest data: We present updated constraints on the free-streaming of warm dark matter\n(WDM) particles derived from an analysis of the Lya flux power spectrum\nmeasured from high-resolution spectra of 25 z > 4 quasars obtained with the\nKeck High Resolution Echelle Spectrometer (HIRES) and the Magellan Inamori\nKyocera Echelle (MIKE) spectrograph. We utilize a new suite of high-resolution\nhydrodynamical simulations that explore WDM masses of 1, 2 and 4 keV (assuming\nthe WDM consists of thermal relics), along with different physically motivated\nthermal histories. We carefully address different sources of systematic error\nthat may affect our final results and perform an analysis of the Lya flux power\nwith conservative error estimates. By using a method that samples the\nmulti-dimensional astrophysical and cosmological parameter space, we obtain a\nlower limit mwdm > 3.3 keV (2sigma) for warm dark matter particles in the form\nof early decoupled thermal relics. Adding the Sloan Digital Sky Survey (SDSS)\nLya flux power spectrum does not improve this limit. Thermal relics of masses 1\nkeV, 2 keV and 2.5 keV are disfavoured by the data at about the 9sigma, 4sigma\nand 3sigma C.L., respectively. Our analysis disfavours WDM models where there\nis a suppression in the linear matter power spectrum at (non-linear) scales\ncorresponding to k=10h/Mpc which deviates more than 10% from a LCDM model.\nGiven this limit, the corresponding \"free-streaming mass\" below which the mass\nfunction may be suppressed is 2x10^8 Msun/h. There is thus very little room for\na contribution of the free-streaming of WDM to the solution of what has been\ntermed the small scale crisis of cold dark matter.", "category": "astro-ph_CO" }, { "text": "The strongest gravitational lenses: I. The statistical impact of cluster\n mergers: For more than a decade now, it has been controversial whether or not the high\nrate of giant gravitational arcs and the largest observed Einstein radii are\nconsistent with the standard cosmological model. Recent studies indicate that\nmergers provide an efficient mechanism to substantially increase the\nstrong-lensing efficiency of individual clusters. Based on purely semi-analytic\nmethods, we investigated the statistical impact of cluster mergers on the\ndistribution of the largest Einstein radii and the optical depth for giant\ngravitational arcs of selected cluster samples. Analysing representative\nall-sky realizations of clusters at redshifts z < 1 and assuming a constant\nsource redshift of z_s = 2.0, we find that mergers increase the number of\nEinstein radii above 10 arcsec (20 arcsec) by ~ 35 % (~ 55 %). Exploiting the\ntight correlation between Einstein radii and lensing cross sections, we infer\nthat the optical depth for giant gravitational arcs with a length-to-width\nratio > 7.5 of those clusters with Einstein radii above 10 arcsec (20 arcsec)\nincreases by ~ 45 % (85 %). Our findings suggest that cluster mergers\nsignificantly influence in particular the statistical lensing properties of the\nstrongest gravitational lenses. We conclude that semi-analytic studies must\ninevitably take these events into account before questioning the standard\ncosmological model on the basis of the largest observed Einstein radii and the\nstatistics of giant gravitational arcs.", "category": "astro-ph_CO" }, { "text": "Very High Energy Active Galactic Nuclei Synchrotron self-Compton\n Modeling Tour: The current very high energy (VHE; E>100GeV) experiments have tremendously\nincreased the number of detected extragalactic sources. We present a\nsynchrotron self-Compton modeling tour of the active galactic nuclei currently\nestablished as VHE emitters so far, and investigate possible correlations among\nthe intrinsic and derived parameters.", "category": "astro-ph_CO" }, { "text": "Modeling the Alignment Profile of Satellite Galaxies in Clusters: Analyzing the halo and galaxy catalogs from the Millennium simulations at\nredshifts $z=0,\\ 0.5,\\ 1$, we determine the alignment profiles of cluster\ngalaxies by measuring the average alignments between the major axes of the\npseudo inertia tensors from all satellites within cluster's virial radius and\nfrom only those satellites within some smaller radius as a function of the\ntop-hat scale difference. The alignment profiles quantify how well the\nsatellite galaxies retain the memory of the external tidal fields after merging\ninto their host clusters and how fast they lose the initial alignment tendency\nas the cluster's relaxation proceeds. It is found that the alignment profile\ndrops faster at higher redshifts and on smaller mass scales. This result is\nconsistent with the picture that the faster merging of the satellites and\nearlier onset of the nonlinear effect inside clusters tend to break the\npreferential alignments of the satellites with the external tidal fields.\nModeling the alignment profile of cluster galaxies as a power-law of the\ndensity correlation coefficient that is independent of the power spectrum\nnormalization ($\\sigma_{8}$) and demonstrating that the density correlation\ncoefficient varies sensitively with the density parameter ($\\Omega_{m}$) and\nneutrino mass fraction ($f_{\\nu}$), we suggest that the alignment profile of\ncluster galaxies might be useful for breaking the $\\Omega_{m}$-$\\sigma_{8}$ and\n$f_{\\nu}$-$\\sigma_{8}$ degeneracies.", "category": "astro-ph_CO" }, { "text": "Searching for Anisotropic Cosmic Birefringence with Polarization Data\n from SPTpol: We present a search for anisotropic cosmic birefringence in 500 deg$^2$ of\nsouthern sky observed at 150 GHz with the SPTpol camera on the South Pole\nTelescope. We reconstruct a map of cosmic polarization rotation anisotropies\nusing higher-order correlations between the observed cosmic microwave\nbackground (CMB) $E$ and $B$ fields. We then measure the angular power spectrum\nof this map, which is found to be consistent with zero. The non-detection is\ntranslated into an upper limit on the amplitude of the scale-invariant cosmic\nrotation power spectrum, $L(L+1)C_L^{\\alpha\\alpha}/2\\pi < 0.10 \\times 10^{-4}$\nrad$^2$ (0.033 deg$^2$, 95% C.L.). This upper limit can be used to place\nconstraints on the strength of primordial magnetic fields, $B_{1 \\rm Mpc} < 17\n{\\rm nG} $ (95% C.L.), and on the coupling constant of the Chern-Simons\nelectromagnetic term $g_{a\\gamma} < 4.0 \\times 10^{-2}/H_I $ (95% C.L.), where\n$H_I$ is the inflationary Hubble scale. For the first time, we also\ncross-correlate the CMB temperature fluctuations with the reconstructed\nrotation angle map, a signal expected to be non-vanishing in certain\ntheoretical scenarios, and find no detectable signal. We perform a suite of\nsystematics and consistency checks and find no evidence for contamination.", "category": "astro-ph_CO" }, { "text": "Large Field Polynomial Inflation: Parameter Space, Predictions and\n (Double) Eternal Nature: Simple monomial inflationary scenarios have been ruled out by recent\nobservations. In this work we revisit the next simplest scenario, a\nsingle--field model where the scalar potential is a polynomial of degree four\nwhich features a concave ``almost'' saddle point. We focus on trans--Planckian\nfield values. We reparametrize the potential, which greatly simplifies the\nprocedure for finding acceptbale model parameters. This allows for the first\ncomprehensive scan of parameter space consistent with recent Planck and\nBICEP/Keck 2018 measurements. Even for trans--Planckian field values the\ntensor--to--scalar ratio $r$ can be as small as $\\mathcal{O}(10^{-8})$, but the\nmodel can also saturate the current upper bound. In contrast to the\nsmall--field version of this model, radiative stability does not lead to strong\nconstraints on the parameters of the inflaton potential. For very large field\nvalues the potential can be approximated by the quartic term; as well known,\nthis allows eternal inflation even for field energy well below the reduced\nPlanck mass $M_{\\rm Pl}$, with Hubble parameter $H \\sim 10^{-2} M_{\\rm Pl}$.\nMore interestingly, we find a region of parameter space that even supports {\\em\ntwo phases of eternal inflation}. The second epoch only occurs if the slope at\nthe would--be saddle point is very small, and has $H \\sim 10^{-5} M_{\\rm Pl}$;\nit can only be realized if $r \\sim 10^{-2}$, within the sensitivity range of\nnext--generation CMB observations.", "category": "astro-ph_CO" }, { "text": "Supernova 2011fe from an Exploding Carbon-Oxygen White Dwarf Star: Type Ia supernovae (SNe Ia) have been used empirically as standardized\ncandles to reveal the accelerating universe even though fundamental details,\nsuch as the nature of the progenitor system and how the star explodes, remained\na mystery. There is consensus that a white dwarf star explodes after accreting\nmatter in a binary system, but the secondary could be anything from a main\nsequence star to a red giant, or even another white dwarf. The uncertainty\nstems from the fact that no recent SN Ia has been discovered close enough to\ndetect the stars before explosion. Here we report early observations of SN\n2011fe (PTF11kly) in M101 at a distance of 6.4 Mpc, the closest SN Ia in the\npast 25 years. We find that the exploding star was likely a carbon-oxygen white\ndwarf, and from the lack of an early shock we conclude that the companion was\nmost likely a main sequence star. Early spectroscopy shows high-velocity oxygen\nthat varies on a time scale of hours and extensive mixing of newly synthesized\nintermediate mass elements in the outermost layers of the supernova. A\ncompanion paper uses pre-explosion images to rule out luminous red giants and\nmost helium stars as companions.", "category": "astro-ph_CO" }, { "text": "Results of optical monitoring of 5 SDSS double QSOs with the Nordic\n Optical Telescope: We present optical R-band light curves of five SDSS double QSOs (SDSS\nJ0903+5028, SDSS J1001+5027, SDSS J1206+4332, SDSS J1353+1138, SDSS J1335+0118)\nobtained from monitoring at the Nordic Optical Telescope (NOT) between\nSeptember 2005 and September 2007. We also present analytical and pixelated\nmodeling of the observed systems. For SDSS J1206+4332, we measured the time\ndelay to be 116 days, which, for a Singular Isothermal Ellipsoid model,\ncorresponds to a Hubble constant of 73 km/s/Mpc. Simultaneous pixeleted\nmodeling of five other systems for which a time delay has now been previously\nmeasured at the NOT leads to H_0 = 61.5 km/s/Mpc. Finally, by comparing\nlightcurves of the two images of each system, suitably shifted by the predicted\nor observed time-delays, we found no evidence for microlensing variability over\nthe course of the monitoring period.", "category": "astro-ph_CO" }, { "text": "Mining the Herschel-ATLAS: submillimeter-selected blazars in equatorial\n fields: The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) provides an\nunprecedented opportunity to search for blazars at sub-mm wavelengths. We\ncross-matched the FIRST radio source catalogue with the 11655 sources brighter\nthan 35 mJy at 500{\\mu}m in the \\sim 135 square degrees of the sky covered by\nthe H-ATLAS equatorial fields at 9 h and 15 h, plus half of the field at 12 h.\nWe found that 379 of the H-ATLAS sources have a FIRST counterpart within 10\narcsec, including 8 catalogued blazars (plus one known blazar that was found at\nthe edge of one the H-ATLAS maps). To search for additional blazar candidates\nwe have devised new diagnostic diagrams and found that known blazars occupy a\nregion of the log(S500{\\mu}m/S350{\\mu}m) vs. log(S500{\\mu}m/S1.4GHz) plane\nseparated from that of the other sub-mm sources with radio counterparts. Using\nthis diagnostic we have selected 12 further candidates that turn out to be\nscattered in the (r-z) vs. (u-r) plane or in the WISE colour-colour diagram\nproposed by Massaro et al. (2012), where known blazars are concentrated in well\ndefined strips. This suggests that the majority of them either are not blazars\nor have spectral energy distributions contaminated by their host galaxies. A\nsignificant fraction of true blazars are found to be hosted by star-forming\ngalaxies. This finding, supported by an analysis of blazars detected in Planck\n545 and 857 GHz bands, is at odds with the notion that blazar hosts are passive\nellipticals and indicates that the sub-mm selection is providing a novel\nprospect on blazar properties. Based on an inspection of the available\nphotometric data, including the WISE all-sky survey, the unpublished VIKING\nsurvey and new radio observations, we tentatively estimate that there are 11\nblazars with synchrotron flux density S500{\\mu}m > 35mJy over the considered\narea. This result already allows us to constrain blazar evolution models.", "category": "astro-ph_CO" }, { "text": "G\u00f6del-type universes and chronology protection in Horava-Lifshitz\n gravity: In the attempts toward a quantum gravity theory, general relativity faces a\nserious difficulty since it is non-renormalizable theory. Ho\\v{r}ava-Lifshitz\ngravity offers a framework to circumvent this difficulty, by sacrificing the\nlocal Lorentz invariance at ultra-high energy scales in exchange of\npower-counting renormalizability. The Lorentz symmetry is expected to be\nrecovered at low and medium energy scales. If gravitation is to be described by\na Ho\\v{r}ava-Lifshitz gravity theory there are a number of issues that ought to\nbe reexamined in its context, including the question as to whether this gravity\nincorporates a chronology protection, or particularly if it allows G\\\"odel-type\nsolutions with violation of causality. We show that Ho\\v{r}ava-Lifshitz gravity\nonly allows hyperbolic G\\\"odel-type space-times whose essential parameters $m$\nand $\\omega$ are in the chronology respecting intervals, excluding therefore\nany noncausal G\\\"odel-type space-times in the hyperbolic class. There emerges\nfrom our results that the famous noncausal G\\\"odel model is not allowed in\nHo\\v{r}ava-Lifshitz gravity. The question as to whether this quantum gravity\ntheory permits hyperbolic G\\\"odel-type solutions in the chronology preserving\ninterval of the essential parameters is also examined. We show that\nHo\\v{r}ava-Lifshitz gravity not only excludes the noncausal G\\\"odel universe,\nbut also rules out any hyperbolic G\\\"odel-type solutions for physically\nwell-motivated perfect-fluid matter content.", "category": "astro-ph_CO" }, { "text": "The HBI in a quasi-global model of the intracluster medium: In this paper we investigate how convective instabilities influence heat\nconduction in the intracluster medium (ICM) of cool-core galaxy clusters. The\nICM is a high-beta, weakly collisional plasma in which the transport of\nmomentum and heat is aligned with the magnetic field. The anisotropy of heat\nconduction, in particular, gives rise to instabilities that can access energy\nstored in a temperature gradient of either sign. We focus on the heat-flux\nbuoyancy-driven instability (HBI), which feeds on the outwardly increasing\ntemperature profile of cluster cool cores. Our aim is to elucidate how the\nglobal structure of a cluster impacts on the growth and morphology of the\nlinear HBI modes when in the presence of Braginskii viscosity, and ultimately\non the ability of the HBI to thermally insulate cores. We employ an idealised\nquasi-global model, the plane-parallel atmosphere, which captures the essential\nphysics -- e.g. the global radial profile of the cluster -- while letting the\nproblem remain analytically tractable. Our main result is that the dominant HBI\nmodes are localised to the the innermost (~<20%) regions of cool cores. It is\nthen probable that, in the nonlinear regime, appreciable field-line insulation\nwill be similarly localised. Thus, while radio-mode feedback appears necessary\nin the central few tens of kpc, heat conduction may be capable of offsetting\nradiative losses throughout most of a cool core over a significant fraction of\nthe Hubble time. Finally, our linear solutions provide a convenient numerical\ntest for the nonlinear codes that tackle the saturation of such convective\ninstabilities in the presence of anisotropic transport.", "category": "astro-ph_CO" }, { "text": "The Case for Standard Irradiated Accretion Disks in Active Galactic\n Nuclei: We analyze the broadband photometric light curves of Seyfert 1 galaxies from\nthe Sergeev et al. (2005) sample and find that a) perturbations propagating\nacross the continuum emitting region are a general phenomenon securely detected\nin most cases, b) it is possible to obtain reliable time-delays between\ncontinuum emission in different wavebands, which are not biased by the\ncontribution of broad emission lines to the signal, and that c) such lags are\nconsistent with the predictions of standard irradiated accretion disk models,\ngiven the optical luminosity of the sources. These findings provide new and\nindependent support for standard accretion disks being responsible for the bulk\nof the (rest) optical emission in low-luminosity active galactic nuclei (AGN).\nWe interpret our lag measurements in individual objects within the framework of\nthis model and estimate the typical mass accretion rate to be <~0.1Msol/yr,\nwith little dependence on the black hole mass. Assuming bolometric corrections\ntypical of type-I sources, we find tentative evidence for the radiative\nefficiency of accretion flows being a rising function of the black hole mass.\nWith upcoming surveys that will regularly monitor the sky, we may be able to\nbetter quantify possible departures from standard self-similar models, and\nidentify other modes of accretion in AGN.", "category": "astro-ph_CO" }, { "text": "Are there cool-core clusters at high-redshift? Chandra results and\n prospects with WFXT: In this contribution we trace the evolution of cool-core clusters out to\nz~1.3 using high-resolution Chandra data of three representative cluster\nsamples spanning different redshift ranges. Our analysis is based on the\nmeasurement of the surface brightness (SB) concentration, c_SB, which strongly\nanti-correlates with the central cooling time and allows us to characterize the\ncool-core strength in low S/N data. We confirm a negative evolution in the\nfraction of cool-core clusters with redshift, in particular for very strong\ncool-cores. Still, we find evidence for a large population of well formed\ncool-cores at z ~ 1. This analysis is potentially very effective in\nconstraining the nature and the evolution of the cool-cores, once large samples\nof high-z clusters will be available. In this respect, we explore the potential\nof the proposed mission Wide Field X-ray Telescope (WFXT) to address this\nscience case. We conclude that WFXT provides the best trade-off of angular\nresolution, sensitivity and covered solid angle in order to discover and fully\ncharacterize the cool-core cluster population up to z=1.5.", "category": "astro-ph_CO" }, { "text": "Research Update on Extreme-Mass-Ratio Inspirals: The inspirals of stellar-mass mass compact objects into massive black holes\nin the centres of galaxies are one of the most important sources of\ngravitational radiation for space-based detectors like LISA or eLISA. These\nextreme-mass-ratio inspirals (EMRIs) will enable an ambitious research program\nwith implications for astrophysics, cosmology, and fundamental physics. This\narticle is a summary of the talks delivered at the plenary session on EMRIs at\nthe 10th International LISA Symposium. It contains research updates on the\nfollowing topics: astrophysics of EMRIs; EMRI science potential; and EMRI\nmodeling.", "category": "astro-ph_CO" }, { "text": "Cosmological consequences of a scalar field with oscillating equation of\n state: A possible solution to the fine-tuning and coincidence problems: We propose a new dark energy model for solving the cosmological fine-tuning\nand coincidence problems. A default assumption is that the fine-tuning problem\ndisappears if we do not interpret dark energy as vacuum energy. The key idea to\nsolving the coincidence problem is that the Universe may have several\nacceleration phases across the whole cosmic history. The specific example we\nstudy is a quintessence model with approximately repeated double exponential\npotential, which only introduces one Planck scale parameter and three\ndimensionless parameters of order unity. The cosmological background evolution\nequations can be recast into a four-dimensional dynamical system and its main\nproperties are discussed in details. Preliminary calculations show that our\nmodel is able to explain the observed cosmic late-time acceleration.", "category": "astro-ph_CO" }, { "text": "Bogoliubov Excited States and the Lyth Bound: We show that Bogoliubov excited scalar and tensor modes do not alleviate\nPlanckian evolution during inflation if one assumes that $r$ and the Bogoliubov\ncoefficients are approximately scale invariant. We constrain the excitation\nparameter for the scalar fluctuations, $\\beta$, and tensor perturbations,\n$\\tilde{\\beta}$, by requiring that there be at least three decades of scale\ninvariance in the scalar and tensor power spectrum. For the scalar fluctuations\nthis is motivated by the observed nearly scale invariant scalar power spectrum.\nFor the tensor fluctuations this assumption may be shown to be valid or invalid\nby future experiments.", "category": "astro-ph_CO" }, { "text": "Formation of disk galaxies in preheated media: a preventative feedback\n model: We introduce a semi-analytic galaxy formation model implementing a\nself-consistent treatment for the hot halo gas configuration and the assembly\nof central disks. Using the model, we explore a preventative feedback model, in\nwhich the circum-halo medium is assumed to be preheated up to a certain entropy\nlevel by early starbursts or other processes, and compare it with an ejective\nfeedback model, in which baryons are first accreted into dark matter halos and\nsubsequently ejected out by feedback. The model demonstrates that when the\nmedium is preheated to an entropy comparable to the halo virial entropy the\nbaryon accretion can be largely reduced and delayed. In addition, the preheated\nmedium can establish an extended low density gaseous halo when it accretes into\nthe dark matter halos, and result in a specific angular momentum of the cooling\ngas large enough to form central disks as extended as those observed. Combined\nwith simulated halo assembly histories, the preventative feedback model can\nreproduce remarkably well a number of observational scaling relations. These\ninclude the cold baryon (stellar plus cold gas) mass fraction-halo mass\nrelations, star formation histories, disk size-stellar mass relation and its\nevolution, and the number density of low-mass galaxies as a function of\nredshift. In contrast, the conventional ejective feedback model fails to\nreproduce these observational trends. Using the model, we demonstrate that the\nproperties of disk galaxies are closely tied to the thermal state of hot halo\ngas and even possibly the circum-halo medium, which suggests that observational\ndata for the disk properties and circum-galactic hot/warm medium may jointly\nprovide interesting constraints for galaxy formation models.", "category": "astro-ph_CO" }, { "text": "Kinematic consistency relations of large-scale structures: We describe how the kinematic consistency relations satisfied by density\ncorrelations of the large-scale structures of the Universe can be derived\nwithin the usual Newtonian framework. These relations express a kinematic\neffect and show how the $(\\ell+n)$-density correlation factors in terms of the\n$n$-point correlation and $\\ell$ linear power spectrum factors, in the limit\nwhere the $\\ell$ soft wave numbers become linear and much smaller than the $n$\nother wave numbers. We describe how these relations extend to multifluid cases.\nIn the standard cosmology, these consistency relations derive from the\nequivalence principle. A detection of their violation would indicate\nnon-Gaussian initial conditions, non-negligible decaying modes, or a\nmodification of gravity that does not converge to General Relativity on large\nscales.", "category": "astro-ph_CO" }, { "text": "Perturbative Resonance in WIMP paradigm and its Cosmological\n Implications on Cosmic Reheating and Primordial Gravitational Wave Detection: We investigate the co-evolution of dark matter (DM) density perturbation and\nmetric perturbation in the WIMP paradigm. Instead of adopting the conventional\nassumption that DM starts out in thermal equilibrium, we propose a simple phase\nof DM production for the WIMP paradigm and extend our analysis to this phase.\nBeing free from the envelop of thermal equilibrium, an amplified perturbative\nresonance between DM density perturbation and scalar modes of metric\nperturbation takes place during the DM production phase, and consequently\nresults in a suppression of the tensor-to-scalar ratio of metric perturbation.\nBy specifying the cosmic background with a typical realization of cosmic\nreheating, we establish a relation between DM particle mass $m_\\chi$ and the\ntensor-to-scalar ratio $r$ in the WIMP paradigm, which also contains two\nreheating parameters, the reheating temperature $T_{R_f}$ and the dissipative\nconstant $\\Gamma_0$. Notably, for a sizeable parameter region of WIMP candidate\nand cosmic reheating, this relation predicts a smaller value of $r$ in\ncomparing with the conventional expectation obtained by assuming DM starts out\nin thermal equilibrium. Once the suppression of $r$ is measured in future\nobservations of primordial gravitational wave in CMB, this relation can be used\nto constrain $m_\\chi$, $T_{R_f}$ and $\\Gamma_0$ in principle.", "category": "astro-ph_CO" }, { "text": "Preparing old and recent radio source tables for the VO age: Current\n status: Independent of established data centers, and partly for my own research, I\nhave been collecting the tabular data from nearly 1500 articles concerned with\nradio sources. Optical character recognition (OCR) was used to recover tables\nfrom nearly 600 of these. Tables from only 44 percent of these articles are\navailable in the CDS or CATS catalog collections. This fraction is 62 percent\nfor articles with over 100 sources. Surprisingly, these fractions are not\nbetter for articles published electronically since 2001, perhaps partly due to\nthe fact that often tabular data are published in formats not useful for direct\nmachine reading. The databases Simbad and NED recognize only about 60 percent\nof the bibliographic references corresponding to the existing electronic radio\nsource lists, and the number of objects associated with these references is\nmuch smaller still. Both, object databases like NED and Simbad, as well as\ncatalog browsers (VizieR, CATS) need to be consulted to obtain the most\ncomplete information on radio sources. More human resources at the data centers\nand better collaboration between authors, referees, editors, publishers, and\ndata centers are required to improve the flow of tabular data from journals to\npublic databases. Current efforts within the Virtual Observatory (VO) project,\nto provide retrieval and analysis tools for different types of published and\narchival data stored at various sites, should be balanced by an equal effort to\nrecover and include large amounts of published data not currently available in\nthis way. If human resources can be found, the data sets collected by the\nauthor will be made available for the preparation of metadata necessary for\ntheir ingression into catalog browsers.", "category": "astro-ph_CO" }, { "text": "Detecting Baryon Acoustic Oscillations in Dark Matter from Kinematic\n Weak Lensing Surveys: We investigate the feasibility of extracting Baryon Acoustic Oscillations\n(BAO) from cosmic shear tomography. We particularly focus on the BAO scale\nprecision that can be achieved by future spectroscopy-based, kinematic weak\nlensing (KWL) surveys \\citep[e.g.,][]{Huff13} in comparison to the traditional\nphotometry-based weak lensing surveys. We simulate cosmic shear tomography data\nof such surveys with a few simple assumptions to focus on the BAO information,\nextract the spacial power spectrum, and constrain the recovered BAO feature.\nDue to the small shape noise and the shape of the lensing kernel, we find that\na Dark Energy Task Force Stage IV version of such KWL survey can detect the BAO\nfeature in dark matter by $3$-$\\sigma$ and measure the BAO scale at the\nprecision level of 4\\% while it will be difficult to detect the feature in\nphotometry-based weak lensing surveys. With a more optimistic assumption, a\nKWL-Stage IV could achieve a $\\sim 2\\%$ BAO scale measurement with\n$4.9$-$\\sigma$ confidence. A built-in spectroscopic galaxy survey within such\nKWL survey will allow cross-correlation between galaxies and cosmic shear,\nwhich will tighten the constraint beyond the lower limit we present in this\npaper and therefore possibly allow a detection of the BAO scale bias between\ngalaxies and dark matter.", "category": "astro-ph_CO" }, { "text": "Galaxy and Mass Assembly (GAMA): Dust obscuration in galaxies and their\n recent star formation histories: We present self-consistent star formation rates derived through pan-spectral\nanalysis of galaxies drawn from the Galaxy and Mass Assembly (GAMA) survey. We\ndetermine the most appropriate form of dust obscuration correction via\napplication of a range of extinction laws drawn from the literature as applied\nto Halpha, [O{II}] and UV luminosities. These corrections are applied to a\nsample of 31,508 galaxies from the GAMA survey at z < 0.35. We consider several\ndifferent obscuration curves, including those of Milky Way, Calzetti (2001) and\nFischera and Dopita (2005) curves and their effects on the observed\nluminosities. At the core of this technique is the observed Balmer decrement,\nand we provide a prescription to apply optimal obscuration corrections using\nthe Balmer decrement. We carry out an analysis of the star formation history\n(SFH) using stellar population synthesis tools to investigate the evolutionary\nhistory of our sample of galaxies as well as to understand the effects of\nvariation in the Initial Mass Function (IMF) and the effects this has on the\nevolutionary history of galaxies. We find that the Fischera and Dopita (2005)\nobscuration curve with an R_{v} value of 4.5 gives the best agreement between\nthe different SFR indicators. The 2200A feature needed to be removed from this\ncurve to obtain complete consistency between all SFR indicators suggesting that\nthis feature may not be common in the average integrated attenuation of galaxy\nemission. We also find that the UV dust obscuration is strongly dependent on\nthe SFR.", "category": "astro-ph_CO" }, { "text": "Far-Infrared Properties of Spitzer-selected Luminous Starbursts: We present SHARC-2 350 micron data on 20 luminous z ~ 2 starbursts with\nS(1.2mm) > 2 mJy from the Spitzer-selected samples of Lonsdale et al. and\nFiolet et al. All the sources were detected, with S(350um) > 25 mJy for 18 of\nthem. With the data, we determine precise dust temperatures and luminosities\nfor these galaxies using both single-temperature fits and models with power-law\nmass--temperature distributions. We derive appropriate formulae to use when\noptical depths are non-negligible. Our models provide an excellent fit to the\n6um--2mm measurements of local starbursts. We find characteristic\nsingle-component temperatures T1 ~ 35.5+-2.2 K and integrated infrared (IR)\nluminosities around 10^(12.9+-0.1) Lsun for the SWIRE-selected sources.\nMolecular gas masses are estimated at 4 x 10^(10) Msun, assuming\nkappa(850um)=0.15 m^2/kg and a submillimeter-selected galaxy (SMG)-like\ngas-to-dust mass ratio. The best-fit models imply >~2 kpc emission scales. We\nalso note a tight correlation between rest-frame 1.4 GHz radio and IR\nluminosities confirming star formation as the predominant power source. The\nfar-IR properties of our sample are indistinguishable from the purely\nsubmillimeter-selected populations from current surveys. We therefore conclude\nthat our original selection criteria, based on mid-IR colors and 24 um flux\ndensities, provides an effective means for the study of SMGs at z ~ 1.5--2.5.", "category": "astro-ph_CO" }, { "text": "Cosmological constraints from large-scale structure growth rate\n measurements: We compile a list of $14$ independent measurements of large-scale structure\ngrowth rate between redshifts $0.067 \\leq z \\leq 0.8$ and use this to place\nconstraints on model parameters of constant and time-evolving\ngeneral-relativistic dark energy cosmologies. With the assumption that gravity\nis well-modeled by general relativity, we discover that growth-rate data\nprovide restrictive cosmological parameter constraints. In combination with\ntype Ia supernova apparent magnitude versus redshift data and Hubble parameter\nmeasurements, the growth rate data are consistent with the standard\nspatially-flat $\\Lambda$CDM model, as well as with mildly evolving dark energy\ndensity cosmological models.", "category": "astro-ph_CO" }, { "text": "On the Contribution of Active Galactic Nuclei to the High-Redshift\n Metagalactic Ionizing Background: Motivated by the claimed detection of a large population of faint active\ngalactic nuclei (AGN) at high redshift, recent studies have proposed models in\nwhich AGN contribute significantly to the z > 4 H I ionizing background. In\nsome models, AGN are even the chief sources of reionization. If correct, these\nmodels would make necessary a complete revision to the standard view that\ngalaxies dominated the high-redshift ionizing background. It has been suggested\nthat AGN-dominated models can better account for two recent observations that\nappear to be in conflict with the standard view: (1) large opacity variations\nin the z ~ 5.5 H I Lyman-alpha forest, and (2) slow evolution in the mean\nopacity of the He II Lyman-alpha forest. Large spatial fluctuations in the\nionizing background from the brightness and rarity of AGN may account for the\nformer, while the earlier onset of He II reionization in these models may\naccount for the latter. Here we show that models in which AGN emissions source\n>~ 50 % of the ionizing background generally provide a better fit to the\nobserved H I Lyman-alpha forest opacity variations compared to standard\ngalaxy-dominated models. However, we argue that these AGN-dominated models are\nin tension with constraints on the thermal history of the intergalactic medium\n(IGM). Under standard assumptions about the spectra of AGN, we show that the\nearlier onset of He II reionization heats up the IGM well above recent\ntemperature measurements. We further argue that the slower evolution of the\nmean opacity of the He II Lyman-alpha forest relative to simulations may\nreflect deficiencies in current simulations rather than favor AGN-dominated\nmodels as has been suggested.", "category": "astro-ph_CO" }, { "text": "Baryonic effects for weak lensing. Part II. Combination with X-ray data\n and extended cosmologies: An accurate modelling of baryonic feedback effects is required to exploit the\nfull potential of future weak-lensing surveys such as Euclid or LSST. In this\nsecond paper in a series of two, we combine Euclid-like mock data of the cosmic\nshear power spectrum with an eROSITA X-ray mock of the cluster gas fraction to\nrun a combined likelihood analysis including both cosmological and baryonic\nparameters. Following the first paper of this series, the baryonic effects\n(based on the baryonic correction model of Schneider et al. 2019) are included\nin both the tomographic power spectrum and the covariance matrix. However, this\ntime we assume the more realistic case of a $\\Lambda$CDM cosmology with massive\nneutrinos, and we consider several extensions of the currently favoured\ncosmological model. For the standard $\\Lambda$CDM case, we show that including\nX-ray data reduces the uncertainties on the sum of the neutrino mass by\n$\\sim30$ percent, while there is only a mild improvement on other parameters\nsuch as $\\Omega_m$ and $\\sigma_8$. As extensions of $\\Lambda$CDM, we consider\nthe cases of a dynamical dark energy model (wCDM), a $f(R)$ gravity model\n(fRCDM), and a mixed dark matter model ($\\Lambda$MDM) with both a cold and a\nwarm/hot dark matter component. We find that combining weak lensing with X-ray\ndata only leads to a mild improvement of the constraints on the additional\nparameters of wCDM, while the improvement is more substantial for both fRCDM\nand $\\Lambda$MDM. Ignoring baryonic effects in the analysis pipeline leads to\nsignificant false-detections of either phantom dark energy or a light\nsubdominant dark matter component. Overall we conclude that for all cosmologies\nconsidered, a general parametrisation of baryonic effects is both necessary and\nsufficient to obtain tight constraints on cosmological parameters.", "category": "astro-ph_CO" }, { "text": "Quasi-evaporating black holes and cold dark matter: Vilkovisky has claimed to have solved the black hole backreaction problem and\nfinds that black holes lose only ten percent of their mass to Hawking radiation\nbefore evaporation ceases. We examine the implications of this scenario for\ncold dark matter, assuming that primordial black holes are created during the\nreheating period after inflation. The mass spectrum is expected to be dominated\nby 10-gram black holes. Nucleosynthesis constraints and the requirement that\nthe earth presently exist do not come close to ruling out such black holes as\ndark matter candidates. They also evade the demand that the photon density\nproduced by evaporating primordial black holes does not exceed the present\ncosmic radiation background by a factor of about one thousand.", "category": "astro-ph_CO" }, { "text": "Doubling Strong Lensing as a Cosmological Probe: Strong gravitational lensing provides a geometric probe of cosmology in a\nunique manner through distance ratios involving the source and lens. This is\nwell known for the time delay distance derived from measured delays between\nlightcurves of the images of variable sources such as quasars. Recently, double\nsource plane lens systems involving two constant sources lensed by the same\nforeground lens have been proposed as another probe, involving a different\nratio of distances measured from the image positions and fairly insensitive to\nthe lens modeling. Here we demonstrate that these two different sets of strong\nlensing distance ratios have strong complementarity in cosmological leverage.\nUnlike other probes, the double source distance ratio is actually more\nsensitive to the dark energy equation of state parameters $w_0$ and $w_a$ than\nto the matter density $\\Omega_m$, for low redshift lenses. Adding double source\ndistance ratio measurements can improve the dark energy figure of merit by 40%\nfor a sample of fewer than 100 low redshift systems, or even better for the\noptimal redshift distribution we derive.", "category": "astro-ph_CO" }, { "text": "Correlation of AGN Jet Power with the Entropy Profile in Cooling Flow\n Clusters: We find that the power of jets that inflate bubble pairs in cooling flow\nclusters of galaxies correlates with the size of the inner region where the\nentropy profile is flat, as well as with the gas mass in that region and the\nentropy floor (the entropy value at the center of the cluster). These\ncorrelations strengthen the cold feedback mechanism that is thought to operate\nin cooling flow clusters and during galaxy formation. In the cold feedback\nmechanism the central super-massive black hole (SMBH) is fed with cold clumps\nthat originate in an extended region of the cooling flow volume, in particular\nfrom the inner region that has a flat entropy profile. Such a process ensures a\ntight feedback between radiative cooling and heating by the SMBH (the AGN). The\nderived expressions should be used instead of the Bondi accretion rate when\nstudying AGN feedback. We find that the mass of molecular gas also correlates\nwith the entropy profile parameters, despite that the jet power does not\ncorrelate with the molecular gas mass. This further suggests that the entropy\nprofile is a fundamental parameter determining cooling and feedback in cooling\nflow clusters.", "category": "astro-ph_CO" }, { "text": "Hubble parameter reconstruction from a principal component analysis:\n minimizing the bias: A model-independent reconstruction of the cosmic expansion rate is essential\nto a robust analysis of cosmological observations. Our goal is to demonstrate\nthat current data are able to provide reasonable constraints on the behavior of\nthe Hubble parameter with redshift, independently of any cosmological model or\nunderlying gravity theory. Using type Ia supernova data, we show that it is\npossible to analytically calculate the Fisher matrix components in a Hubble\nparameter analysis without assumptions about the energy content of the\nUniverse. We used a principal component analysis to reconstruct the Hubble\nparameter as a linear combination of the Fisher matrix eigenvectors (principal\ncomponents). To suppress the bias introduced by the high redshift behavior of\nthe components, we considered the value of the Hubble parameter at high\nredshift as a free parameter. We first tested our procedure using a mock sample\nof type Ia supernova observations, we then applied it to the real data compiled\nby the Sloan Digital Sky Survey (SDSS) group. In the mock sample analysis, we\ndemonstrate that it is possible to drastically suppress the bias introduced by\nthe high redshift behavior of the principal components. Applying our procedure\nto the real data, we show that it allows us to determine the behavior of the\nHubble parameter with reasonable uncertainty, without introducing any ad-hoc\nparameterizations. Beyond that, our reconstruction agrees with completely\nindependent measurements of the Hubble parameter obtained from red-envelope\ngalaxies.", "category": "astro-ph_CO" }, { "text": "A new catalogue of polar-ring galaxies selected from the SDSS: (Abridged) Galaxies with polar rings (PRGs) are a unique class of\nextragalactic objects allowing to investigate a wide range of problems, linked\nwith the formation and evolution of galaxies, and to study the properties of\ntheir dark haloes. The progress in the study of PRGs is constrained by a small\nnumber of known objects of this type. Up to date, we can only attribute about\ntwo dozens of kinematically-confirmed galaxies to this class, mostly from\nWhitmore et al. (1990) catalogue. We present a new catalogue of PRGs based on\nthe results of the original Galaxy Zoo project. Based on the preliminary\nclassification of the Galaxy Zoo, we viewed more than 40000 images of the Sloan\nDigital Sky Survey (SDSS) and selected 275 galaxies, included in our catalogue.\nOur Sloan-based Polar Ring Catalog (SPRC) contains 70 galaxies that we\nclassified as \"the best candidates\", among which we expect to have a very high\nproportion of true PRGs, and 115 good PRG candidates. 53 galaxies are\nclassified as PRG related objects.We identified 37 galaxies that have their\npresumed polar rings seen almost face-on. The SPRC objects are on the average\nfainter and located further away than the galaxies from the catalog by Whitmore\net al., although our catalogue does include dozens of new nearby candidate\nPRGs. The new catalogue significantly increases the number of genuine PRG\ncandidates, and may serve as a good basis both for the further detailed study\nof individual galaxies, and for the statistical analysis of PRGs as a separate\nclass of objects. We performed spectroscopic observations of six galaxies from\nthe SPRC at the 6-m telescope. The existence of polar rings was confirmed in\nfive galaxies, and one object appeared to be a projection of a pair of\ngalaxies. Adding the literature data, we can already classify 10 galaxies from\nour catalogue to the kinematically-confirmed PRGs.", "category": "astro-ph_CO" }, { "text": "Cosmic Radio Background from Primordial Black Holes at Cosmic Dawn: The presence of an extra radio background besides the cosmic microwave\nbackground has important implications for the observation of the 21-cm signal\nduring the cosmic Dark Ages, Cosmic Dawn, and epoch of Reionization. The strong\nabsorption trough found in the 21-cm global spectrum measured by the EDGES\nexperiment, which has a much greater depth than the standard model prediction,\nhas drawn great interest to this scenario, but more generally it is still of\ngreat interest to consider such a cosmic radio background (CRB) in the early\nUniverse. To be effective in affecting the 21-cm signal at early time, such a\nradio background must be produced by sources which can emit strong radio\nsignals but modest amount of X-rays, so that the gas is not heated up too\nearly. We investigate the scenario that such a radio background is produced by\nthe primordial black holes (PBHs). For PBH with a single mass, we find that if\nthe PBHs' abundance $\\log(f_{\\rm PBH})$ (ratio of total PBH mass density to\ntotal matter density) and mass satisfy the relation $\\log(f_{\\rm PBH}) \\sim\n-1.8\\log(M_\\bullet/{\\rm M}_{\\odot})-3.5$ for $1\\,{\\rm M}_\\odot \\lesssim\nM_\\bullet \\lesssim 300 {\\rm M}_\\odot$, and have jet emission, they can generate\na CRB required for reproducing the 21-cm absorption signal seen by the EDGES.\nThe accretion rate can be boosted if the PBHs are surrounded by dark matter\nhalos, which permits lower $f_{\\rm PBH}$ value to satisfy the EDGES\nobservation. In the latter scenario, since the accretion rate can evolve\nrapidly during the Cosmic Dawn, the frequency (redshift) and depth of the\nabsorption trough can determine the mass and abundance of the PBHs\nsimultaneously. For absorption trough redshift $\\sim$ 17 and depth $\\sim -500$\nmK, it corresponds to $M_\\bullet \\sim 1.05\\,{\\rm M}_{\\odot}$ and $f_{\\rm\nPBH}\\sim 1.5\\times10^{-4}$.", "category": "astro-ph_CO" }, { "text": "HST Morphologies of z ~ 2 Dust-Obscured Galaxies II: Bump Sources: We present Hubble Space Telescope (HST) imaging of 22 ultra-luminous infrared\ngalaxies (ULIRGs) at z~2 with extremely red R-[24] colors (called dust-obscured\ngalaxies, or DOGs) which have a local maximum in their spectral energy\ndistribution (SED) at rest-frame 1.6um associated with stellar emission. These\nsources, which we call \"bump DOGs\", have star-formation rates of 400-4000\nMsun/yr and have redshifts derived from mid-IR spectra which show strong\npolycyclic aromatic hydrocarbon emission --- a sign of vigorous on-going\nstar-formation. Using a uniform morphological analysis, we look for\nquantifiable differences between bump DOGs, power-law DOGs (Spitzer-selected\nULIRGs with mid-IR SEDs dominated by a power-law and spectral features that are\nmore typical of obscured active galactic nuclei than starbursts),\nsub-millimeter selected galaxies (SMGs), and other less-reddened ULIRGs from\nthe Spitzer extragalactic First Look Survey (XFLS). Bump DOGs are larger than\npower-law DOGs (median Petrosian radius of 8.4 +/- 2.7 kpc vs. 5.5 +/- 2.3 kpc)\nand exhibit more diffuse and irregular morphologies (median M_20 of -1.08 +/-\n0.05 vs. -1.48 +/- 0.05). These trends are qualitatively consistent with\nexpectations from simulations of major mergers in which merging systems during\nthe peak star-formation rate period evolve from M_20 = -1.0 to M_20 = -1.7.\nLess obscured ULIRGs (i.e., non-DOGs) tend to have more regular, centrally\npeaked, single-object morphologies rather than diffuse and irregular\nmorphologies. This distinction in morphologies may imply that less obscured\nULIRGs sample the merger near the end of the peak star-formation rate period.\nAlternatively, it may indicate that the intense star-formation in these\nless-obscured ULIRGs is not the result of a recent major merger.", "category": "astro-ph_CO" }, { "text": "Cosmological Evolution With Interaction Between Dark Energy And Dark\n Matter: In this review we consider in detail different theoretical topics associated\nwith interaction in the dark sector. We study linear and nonlinear interactions\nwhich depend on the dark matter and dark energy densities. We consider a number\nof different models (including the holographic dark energy and dark energy in a\nfractal universe) with interacting dark energy (DE) and dark matter (DM), have\ndone a thorough analysis of these models. The main task of this review was not\nonly to give an idea about the modern set of different models of dark energy,\nbut to show how much can be diverse dynamics of the universe in these models.\nWe find that the dynamics of a Universe that contains interaction in the dark\nsector can differ significantly from the Standard Cosmological Model (SCM).", "category": "astro-ph_CO" }, { "text": "A Density Independent Formulation of Smoothed Particle Hydrodynamics: The standard formulation of the smoothed particle hydrodynamics (SPH) assumes\nthat the local density distribution is differentiable. This assumption is used\nto derive the spatial derivatives of other quantities. However, this assumption\nbreaks down at the contact discontinuity. At the contact discontinuity, the\ndensity of the low-density side is overestimated while that of the high-density\nside is underestimated. As a result, the pressure of the low (high) density\nside is over (under) estimated. Thus, unphysical repulsive force appears at the\ncontact discontinuity, resulting in the effective surface tension. This tension\nsuppresses fluid instabilities. In this paper, we present a new formulation of\nSPH, which does not require the differentiability of density. Instead of the\nmass density, we adopt the internal energy density (pressure), and its\narbitrary function, which are smoothed quantities at the contact discontinuity,\nas the volume element used for the kernel integration. We call this new\nformulation density independent SPH (DISPH). It handles the contact\ndiscontinuity without numerical problems. The results of standard tests such as\nthe shock tube, Kelvin-Helmholtz and Rayleigh-Taylor instabilities, point like\nexplosion, and blob tests are all very favorable to DISPH. We conclude that\nDISPH solved most of known difficulties of the standard SPH, without\nintroducing additional numerical diffusion or breaking the exact force symmetry\nor energy conservation. Our new SPH includes the formulation proposed by\nRitchie & Thomas (2001) as a special case. Our formulation can be extended to\nhandle a non-ideal gas easily.", "category": "astro-ph_CO" }, { "text": "Neutrino clustering around spherical dark matter halos: Cold dark matter halos form within a smoothly distributed background of relic\nneutrinos -- at least some of which are massive and non-relativistic at late\ntimes. We calculate the accumulation of massive neutrinos around spherically\ncollapsing cold dark matter halos in a cosmological background. We identify the\nphysical extent of the \"neutrino halo\" in the spherical collapse model, which\nis large in comparison with the virial radius of the dark matter, and\nconditions under which neutrinos reaching the cold dark matter halo will remain\nbound to the halo at late times. We calculate the total neutrino mass and bound\nneutrino mass associated with isolated spherical halos for several neutrino\nmass hierarchies and provide fitting formulae for these quantities in terms of\nthe cold dark matter halo mass and the masses of the individual neutrino\nspecies.", "category": "astro-ph_CO" }, { "text": "zCOSMOS 20k: Satellite galaxies are the main drivers of environmental\n effects in the galaxy population at least to z~0.7: We explore the role of environment in the evolution of galaxies over\n0.10.04\\,h/$Mpc. Moreover, cosmic magnification\nmeasurements based on an FP could be severely contaminated over a wide range of\nscales by the intrinsic FP correlations.", "category": "astro-ph_CO" }, { "text": "Cosmology of Single Species Hidden Dark Matter: Cosmology and astrophysics provide various ways to study the properties of\ndark matter even if they have negligible non-gravitational interactions with\nthe Standard Model particles and remain hidden. We study a type of hidden dark\nmatter model in which the dark matter is completely decoupled from the Standard\nModel sector except gravitationally, and consists of a single species with a\nconserved comoving particle number. This category of hidden dark matter\nincludes models that act as warm dark matter but is more general. In\nparticular, in addition to having an independent temperature from the Standard\nModel sector, it includes cases in which dark matter is in its own thermal\nequilibrium or is free-streaming, obeys fermionic or bosonic statistics, and\nprocesses a chemical potential that controls the particle occupation number.\nWhile the usual parameterization using the free-streaming scale or the particle\nmass no longer applies, we show that all cases can be well approximated by a\nset of functions parameterized by only one parameter as long as the chemical\npotential is nonpositive: the characteristic scale factor at the time of the\nrelativistic-to-nonrelativistic transition. We study the constraints from Big\nBang Nucleosynthesis, the cosmic microwave background, the Lyman-$\\alpha$\nforest, and the smallest halo mass. We show that the most significant\nphenomenological impact is the suppression of the small-scale matter power\nspectrum -- a typical feature when the dark matter has a velocity dispersion or\npressure at early times. So far, small dark matter halos provide the strongest\nconstraint, limiting the transition scale factor to be no larger than\n$\\sim1.4\\times10^{-4}$ times the scale factor at matter-radiation equality.", "category": "astro-ph_CO" }, { "text": "Weighing neutrinos in $f(R)$ gravity in light of BICEP2: We constrain the neutrino mass in $f(R)$ gravity using the latest\nobservations from the Planck, BAO and BICEP2 data. We find that the measurement\non the B-modes can break the degeneracy between the massive neutrinos and the\n$f(R)$ gravity. We find a non-zero value of the Compton wavelengths $B_{0}$ at\na $68\\%$ confidence level for the $f(R)$ model in the presence of massive\nneutrinos when the BICEP2 data is used. Furthermore, the tension on the\ntensor-to-scalar ratios between the measured values from Plank and BICEP2 is\nsignificantly reconciled in our model.", "category": "astro-ph_CO" }, { "text": "Complementary Cosmological Simulations: Cosmic variance limits the accuracy of cosmological N-body simulations,\nintroducing bias in statistics such as the power spectrum, halo mass function,\nor the cosmic shear. We provide new methods to measure and reduce the effect of\ncosmic variance in existing and new simulations. We ran pairs of simulations\nusing phase-shifted initial conditions with matching amplitudes. We set the\ninitial amplitudes of the Fourier modes to ensure that the average power\nspectrum of the pair is equal to the cosmic mean power spectrum from linear\ntheory. The average power spectrum of a pair of such simulations remains\nconsistent with the estimated nonlinear spectra of the state-of-the-art methods\neven at late times. We also show that the effect of cosmic variance on any\nanalysis involving a cosmological simulation can be estimated using the\ncomplementary pair of the original simulation. To demonstrate the effectiveness\nof our novel technique, we simulated a complementary pair of the original\nMillennium run and quantified the degree to which cosmic variance affected its\nthe power spectrum. The average power spectrum of the original and\ncomplementary Millennium simulation was able to directly resolve the baryon\nacoustic oscillation features.", "category": "astro-ph_CO" }, { "text": "The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A\n Simple Hierarchical Bayesian Model: Conventional Type Ia supernova (SN Ia) cosmology analyses currently use a\nsimplistic linear regression of magnitude versus color and light curve shape,\nwhich does not model intrinsic SN Ia variations and host galaxy dust as\nphysically distinct effects, resulting in low color-magnitude slopes. We\nconstruct a probabilistic generative model for the dusty distribution of\nextinguished absolute magnitudes and apparent colors as the convolution of a\nintrinsic SN Ia color-magnitude distribution and a host galaxy dust\nreddening-extinction distribution. If the intrinsic color-magnitude ($M_B$ vs.\n$B-V$) slope $\\beta_{int}$ differs from the host galaxy dust law $R_B$, this\nconvolution results in a specific curve of mean extinguished absolute magnitude\nvs. apparent color. The derivative of this curve smoothly transitions from\n$\\beta_{int}$ in the blue tail to $R_B$ in the red tail of the apparent color\ndistribution. The conventional linear fit approximates this effective curve\nnear the average apparent color, resulting in an apparent slope $\\beta_{app}$\nbetween $\\beta_{int}$ and $R_B$. We incorporate these effects into a\nhierarchical Bayesian statistical model for SN Ia light curve measurements, and\nanalyze a dataset of SALT2 optical light curve fits of 248 nearby SN Ia at z <\n0.10. The conventional linear fit obtains $\\beta_{app} \\approx 3$. Our model\nfinds a $\\beta_{int} = 2.3 \\pm 0.3$ and a distinct dust law of $R_B = 3.8 \\pm\n0.3$, consistent with the average for Milky Way dust, while correcting a\nsystematic distance bias of $\\sim 0.10$ mag in the tails of the apparent color\ndistribution. Finally, we extend our model to examine the SN Ia luminosity-host\nmass dependence in terms of intrinsic and dust components.", "category": "astro-ph_CO" }, { "text": "Radio selection of the most distant galaxy clusters: We show that the most distant X-ray detected cluster known to date, ClJ1001\nat z=2.506, hosts a strong overdensity of radio sources. Six of them are\nindividually detected (within 10\") in deep 0.75\" resolution VLA 3GHz imaging,\nwith S(3GHz)>8uJy. Of the six, AGN likely affects the radio emission in two\ngalaxies while star formation is the dominant source powering the remaining\nfour. We searched for cluster candidates over the full COSMOS 2-square degree\nfield using radio-detected 3GHz sources and looking for peaks in Sigma5 density\nmaps. ClJ1001 is the strongest overdensity by far with >10sigma, with a simple\nz_phot>1.5 preselection. A cruder photometric rejection of z<1 radio\nforegrounds leaves ClJ1001 as the second strongest overdensity, while even\nusing all radio sources ClJ1001 remains among the four strongest projected\noverdensities. We conclude that there are great prospects for future, deep and\nwide-area radio surveys to discover large samples of the first generation of\nforming galaxy clusters. In these remarkable structures widespread star\nformation and AGN activity of massive galaxy cluster members, residing within\nthe inner cluster core, will ultimately lead to radio continuum as one of the\nmost effective means for their identification, with detection rates expected in\nthe ballpark of 0.1-1 per square degree at z>2.5. Samples of hundreds such\nhigh-redshift clusters could potentially constrain cosmological parameters and\ntest cluster and galaxy formation models.", "category": "astro-ph_CO" }, { "text": "Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies: We review the observed demographics and inferred evolution of supermassive\nblack holes (BHs) found by dynamical modeling of spatially resolved kinematics.\nMost influential was the discovery of a tight correlation between BH mass and\nthe velocity dispersion of the host-galaxy bulge. It and other correlations led\nto the belief that BHs and bulges coevolve by regulating each other's growth.\nNew results are now replacing this simple story with a richer and more\nplausible picture in which BHs correlate differently with different galaxy\ncomponents. BHs are found in pure-disk galaxies, so classical\n(elliptical-galaxy-like) bulges are not necessary to grow BHs. But BHs do not\ncorrelate with galaxy disks. And any correlations with disk-grown pseudobulges\nor halo dark matter are so weak as to imply no close coevolution. We suggest\nthat there are four regimes of BH feedback. 1- Local, stochastic feeding of\nsmall BHs in mainly bulgeless galaxies involves too little energy to result in\ncoevolution. 2- Global feeding in major, wet galaxy mergers grows giant BHs in\nshort, quasar-like \"AGN\" events whose feedback does affect galaxies. This makes\nclassical bulges and coreless-rotating ellipticals. 3- At the highest BH\nmasses, maintenance-mode feedback into X-ray gas has the negative effect of\nhelping to keep baryons locked up in hot gas. This happens in giant,\ncore-nonrotating ellipticals. They inherit coevolution magic from smaller\nprogenitors. 4- Independent of any feedback physics, the averaging that results\nfrom successive mergers helps to engineer tight BH correlations.", "category": "astro-ph_CO" }, { "text": "Relationship between the CMB, SZ Cluster Counts, and Local Hubble\n Parameter Measurements in a Simple Void Model: The discrepancy between the amplitudes of matter fluctuations inferred from\nSunyaev-Zel'dovich (SZ) cluster number counts, the primary temperature, and the\npolarization anisotropies of the cosmic microwave background (CMB) measured by\nthe Planck satellite can be reconciled if the local universe is embedded in an\nunder-dense region as shown by Lee, 2014. Here using a simple void model\nassuming the open Friedmann-Robertson-Walker geometry and a Markov Chain Monte\nCarlo technique, we investigate how deep the local under-dense region needs to\nbe to resolve this discrepancy. Such local void, if exists, predicts the local\nHubble parameter value that is different from the global Hubble constant. We\nderive the posterior distribution of the local Hubble parameter from a joint\nfitting of the Planck CMB data and SZ cluster number counts assuming the simple\nvoid model. We show that the predicted local Hubble parameter value of $H_{\\rm\nloc}=70.1\\pm0.34~{\\rm km\\,s^{-1}Mpc^{-1}}$ is in better agreement with direct\nlocal Hubble parameter measurements, indicating that the local void model may\nprovide a consistent solution to the cluster number counts and Hubble parameter\ndiscrepancies.", "category": "astro-ph_CO" }, { "text": "Color and stellar population gradients in galaxies. Correlation with\n mass: We analyze the color gradients (CGs) of ~50000 nearby SDSS galaxies. From\nsynthetic spectral models based on a simplified star formation recipe, we\nderive the mean spectral properties, and explain the observed radial trends of\nthe color as gradients of the stellar population age and metallicity (Z). The\nmost massive ETGs (M_* > 10^{11} Msun) have shallow CGs in correspondence of\nshallow (negative) Z gradients. In the stellar mass range 10^(10.3-10.5) < M_*\n< 10^(11) Msun, the Z gradients reach their minimum of ~ -0.5 dex^{-1}. At M_*\n~ 10^{10.3-10.5} Msun, color and Z gradient slopes suddenly change. They turn\nout to anti-correlate with the mass, becoming highly positive at the very low\nmasses. We have also found that age gradients anti-correlate with Z gradients,\nas predicted by hierarchical cosmological simulations for ETGs. On the other\nside, LTGs have gradients which systematically decrease with mass (and are\nalways more negative than in ETGs), consistently with the expectation from gas\ninfall and SN feedback scenarios. Z is found to be the main driver of the trend\nof color gradients, especially for LTGs, but age gradients are not negligible\nand seem to play a significant role too. We have been able to highlight that\nolder galaxies have systematically shallower age and Z gradients than younger\nones. Our results for high-mass galaxies are in perfect agreement with\npredictions based on the merging scenario, while the evolution of LTGs and\nyounger and less massive ETGs seems to be mainly driven by infall and SN\nfeedback. (Abridged)", "category": "astro-ph_CO" }, { "text": "Dark matter profiles of SPARC galaxies: a challenge to fuzzy dark matter: Stellar and gas kinematics of galaxies are a sensitive probe of the dark\nmatter distribution in the halo. The popular fuzzy dark matter models predict\nthe peculiar shape of density distribution in galaxies: specific dense core\nwith sharp transition to the halo. Moreover, fuzzy dark matter predicts scaling\nrelations between the dark matter particle mass and density parameters. In this\nwork, we use a Bayesian framework and several dark matter halo models to\nanalyse the stellar kinematics of galaxies using the Spitzer Photometry and\nAccurate Rotation Curves database. We then employ a Bayesian model comparison\nto select the best halo density model. We find that more than half of the\ngalaxies prefer the fuzzy dark model against standard dark matter profiles\n(NFW, Burkert, and cored NFW). While this seems like a success for fuzzy dark\nmatter, we also find that there is no single value for the particle mass that\nprovides a good fit for all galaxies.", "category": "astro-ph_CO" }, { "text": "Bounds from ISW-galaxy cross-correlations on generalized covariant\n Galileon models: Several modified cosmological models exist, which also try to address the\ntensions between data and predictions of the $\\Lambda$-CDM model. Galileon\nmodels are particular scalar tensor theories that represent one such\npossibilities. While it is commonly understood that there may be\ninconsistencies between predictions of some Galileon models and observations,\nin particular concerning ISW-galaxy cross-correlations, there is no proof yet\nthat these models are completely ruled out. Indeed, by using a specific\nbackground in the generalized covariant Galileon theory known as the the\ntracker solution, here we show that, after imposing all standard theoretical\nstability constraints, it is still possible to identify a region in the\nparameter space of the model that allows for positive ISW-galaxy\ncross-correlations. By a physical interpretation in terms of a chi-square\nanalysis, we confirm the expectation that in this viable region the predictions\nof generalized covariant Galileon theory on the tracker solution background\nhave higher likelihood when they approach the physics of the $\\Lambda$-CDM\nmodel.", "category": "astro-ph_CO" }, { "text": "The Dark Matter Density in the Solar Neighborhood reconsidered: Both the gas flaring and the dip in the rotation curve, which was recently\nreconfirmed with precise measurements using the VERA VLBI array in Japan,\nsuggest doughnut-like substructure in the dark matter (DM) halo. A global fit\nto all available data shows that the data are indeed best described by an NFW\nDM profile complemented by two doughnut-like DM substructures with radii of 4.2\nand 12.4 kpc, which coincide with the local dust ring and the Monocerus ring of\nstars, respectively. Both regions have been suggested as regions with tidal\nstreams from \"shredded\" satellites. If real, the radial extensions of these\nnearby ringlike structures enhance the local dark matter density by a factor of\nfour to about 1.3$\\pm0.3$ GeV/cm$^3$.\n It is shown that i) this higher DM density is perfectly consistent with the\nlocal gravitational potential determining the surface density and the local\nmatter density (Oort limit), ii) previous determinations of the surface density\nwere biased by the assumption of a smoothly varying DM halo and iii) the\ns-shaped gas flaring is explained. Such a possible enhancement of the local DM\ndensity is of great interest for direct DM searches and would change the\ndirectional dependence for indirect DM searches.", "category": "astro-ph_CO" }, { "text": "On the Evolution of the Cores of Radio Sources and Their Extended Radio\n Emission: The work in this paper aims at determining the evolution and possible\nco-evolution of radio-loud active galactic nuclei (AGNs) and their cores via\ntheir radio luminosity functions (i.e., total and core RLF respectively). Using\na large combined sample of 1063 radio-loud AGNs selected at low radio\nfrequency, we investigate the radio luminosity function (RLF) at 408 MHz of\nsteep-spectrum radio sources. Our results support a luminosity-dependent\nevolution. Using core flux density data of the complete sample 3CRR, we\ninvestigate the core RLF at 5.0 GHz. Based on the combined sample with\nincomplete core flux data, we also estimate the core RLF using a modified\nfactor of completeness. Both results are consistent and show that the comoving\nnumber density of radio cores displays a persistent decline with redshift,\nimplying a negative density evolution. We find that the core RLF is obviously\ndifferent from the total RLF at 408 MHz band which is mainly contributed by\nextended lobes, implying that the cores and extended lobes could not be\nco-evolving at radio emission.", "category": "astro-ph_CO" }, { "text": "Evaluating the Calorimeter Model with Broadband, Continuous Spectra of\n Starburst Galaxies Observed with the Allen Telescope Array: Although the relationship between the far-infrared and cm-wave radio\nluminosities of normal galaxies is one of the most striking correlations in\nastronomy, a solid understanding of its physical basis is lacking. In one\ninterpretation, the \"calorimeter model,\" rapid synchrotron cooling of cosmic\nray electrons is essential in reproducing the observed linear relationship.\nObserved radio spectra, however, are shallower than what is expected of cooled\nsynchrotron emission. In Thompson et al. (2006), a simple parameterized model\nis presented to explain how relatively shallow observed spectra might arise\neven in the presence of rapid synchrotron cooling by accounting for ionization\nlosses and other cooling mechanisms. During the commissioning of the 42-element\nAllen Telescope Array, we observed the starburst galaxies M82, NGC 253, and Arp\n220 at frequencies ranging from 1 to 7 GHz, obtaining unprecedented broadband\ncontinuous radio spectra of these sources. We combine our observations with\nhigh-frequency data from the literature to separate the spectra into thermal\nand nonthermal components. The nonthermal components all steepen in the cm-wave\nregime and cannot be well-modeled as simple power laws. The model of Thompson\net al. is consistent with our M82 results when plausible parameters are chosen,\nand our results in fact significantly shrink the space of allowed model\nparameters. The model is only marginally consistent with our NGC 253 data.\nAssuming the Thompson et al. model, a steep electron energy injection index of\np = -2.5 is ruled out in M82 and NGC 253 to >99% confidence. We describe in\ndetail the observing procedures, calibration methods, analysis, and consistency\nchecks used for broadband spectral observations with the Allen Telescope Array.", "category": "astro-ph_CO" }, { "text": "Magnetic field amplification by shocks in galaxy clusters: application\n to radio relics: Merger shocks induce turbulence in the intra-cluster medium (ICM), and, under\nsome circumstances, accelerate electrons to relativistic velocities to form\nso-called radio relics. Relics are mostly found at the periphery of galaxy\nclusters and appear to have magnetic fields at the microGauss level. Here we\ninvestigate the possible origins of these magnetic fields. Turbulence produced\nby the shock itself cannot explain the magnitude of these fields. However, we\nargue that if the turbulent pressure support in the ICM upstream of the merger\nshock is of the order of 10 to 30 percent of the total pressure on scales of a\nfew times 100 kpc, then vorticity generated by compressive and baroclinic\neffects across the shock discontinuity can lead to a sufficient amplification\nof the magnetic field. Compressional amplification can explain the large\npolarisation of the radio emission more easily than dynamo turbulent\namplification. Finally, clumping of the ICM is shown to have a negligible\neffect on magnetic field amplification.", "category": "astro-ph_CO" }, { "text": "The Nature of the Warm/Hot Intergalactic Medium I. Numerical Methods,\n Convergence, and OVI Absorption: We perform a series of cosmological simulations using Enzo, an Eulerian\nadaptive-mesh refinement, N-body + hydrodynamical code, applied to study the\nwarm/hot intergalactic medium. The WHIM may be an important component of the\nbaryons missing observationally at low redshift. We investigate the dependence\nof the global star formation rate and mass fraction in various baryonic phases\non spatial resolution and methods of incorporating stellar feedback. Although\nboth resolution and feedback significantly affect the total mass in the WHIM,\nall of our simulations find that the WHIM fraction peaks at z ~ 0.5, declining\nto 35-40% at z = 0. We construct samples of synthetic OVI absorption lines from\nour highest-resolution simulations, using several models of oxygen ionization\nbalance. Models that include both collisional ionization and photoionization\nprovide excellent fits to the observed number density of absorbers per unit\nredshift over the full range of column densities (10^13 cm-2 <= N_OVI <= 10^15\ncm^-2). Models that include only collisional ionization provide better fits for\nhigh column density absorbers (N_OVI > 10^14 cm^-2). The distribution of OVI in\ndensity and temperature exhibits two populations: one at T ~ 10^5.5 K\n(collisionally ionized, 55% of total OVI) and one at T ~ 10^4.5 K\n(photoionized, 37%) with the remainder located in dense gas near galaxies.\nWhile not a perfect tracer of hot gas, OVI provides an important tool for a\nWHIM baryon census.", "category": "astro-ph_CO" }, { "text": "Environmental dependence of bulge-dominated galaxy sizes in hierarchical\n models of galaxy formation. Comparison with the local Universe: We compare state-of-the-art semi-analytic models of galaxy formation as well\nas advanced sub-halo abundance matching models with a large sample of\nearly-type galaxies from SDSS at z < 0.3. We focus our attention on the\ndependence of median sizes of central galaxies on host halo mass. The data do\nnot show any difference in the structural properties of early-type galaxies\nwith environment, at fixed stellar mass. All hierarchical models considered in\nthis work instead tend to predict a moderate to strong environmental\ndependence, with the median size increasing by a factor of about 1.5-3 when\nmoving from low to high mass host haloes. At face value the discrepancy with\nthe data is highly significant, especially at the cluster scale, for haloes\nabove log Mhalo > 14. The convolution with (correlated) observational errors\nreduces some of the tension. Despite the observational uncertainties, the data\ntend to disfavour hierarchical models characterized by a relevant contribution\nof disc instabilities to the formation of spheroids, strong gas dissipation in\n(major) mergers, short dynamical friction timescales, and very short quenching\ntimescales in infalling satellites. We also discuss a variety of additional\nrelated issues, such as the slope and scatter in the local size-stellar mass\nrelation, the fraction of gas in local early-type galaxies, and the general\npredictions on satellite galaxies.", "category": "astro-ph_CO" }, { "text": "Starlet l1-norm for weak lensing cosmology: We present a new summary statistic for weak lensing observables, higher than\nsecond order, suitable for extracting non-Gaussian cosmological information and\ninferring cosmological parameters. We name this statistic the 'starlet\n$\\ell_1$-norm' as it is computed via the sum of the absolute values of the\nstarlet (wavelet) decomposition coefficients of a weak lensing map. In\ncomparison to the state-of-the-art higher-order statistics -- weak lensing peak\ncounts and minimum counts, or the combination of the two -- the $\\ell_1$-norm\nprovides a fast multi-scale calculation of the full void and peak distribution,\navoiding the problem of defining what a peak is and what a void is: The\n$\\ell_1$-norm carries the information encoded in all pixels of the map, not\njust the ones in local maxima and minima. We show its potential by applying it\nto the weak lensing convergence maps provided by the MassiveNus simulations to\nget constraints on the sum of neutrino masses, the matter density parameter,\nand the amplitude of the primordial power spectrum. We find that, in an ideal\nsetting without further systematics, the starlet $\\ell_1$-norm remarkably\noutperforms commonly used summary statistics, such as the power spectrum or the\ncombination of peak and void counts, in terms of constraining power,\nrepresenting a promising new unified framework to simultaneously account for\nthe information encoded in peak counts and voids. We find that the starlet\n$\\ell_1$-norm outperforms the power spectrum by $72\\%$ on M$_{\\nu}$, $60\\%$ on\n$\\Omega_{\\rm m}$, and $75\\%$ on $A_{\\rm s}$ for the Euclid-like setting\nconsidered; it also improves upon the state-of-the-art combination of peaks and\nvoids for a single smoothing scale by $24\\%$ on M$_{\\nu}$, $50\\%$ on\n$\\Omega_{\\rm m}$, and $24\\%$ on $A_{\\rm s}$.", "category": "astro-ph_CO" }, { "text": "X-ray measurement of the elemental abundances at the outskirts of the\n Perseus cluster with Suzaku: We report on the abundance of metals (Mg and Fe) in the intracluster medium\n(ICM) at the outskirts (0.2 r200 - 0.8 r200) of the Perseus cluster. The X-ray\nspectra were obtained in the Suzaku/XIS mapping observations of this region. We\nemploy single temperature models to fit all the X-ray spectra. The ICM\ntemperature smoothly decreases toward the outer region from 6 keV to 4 keV. The\nFe abundance is uniformly distributed at the outskirts (~0.3 solar). The Mg\nabundance is ~1 solar at the outskirts. The solar ratios of Mg/Fe of the\noutskirts region (Mg/Fe ~4) are a factor of 4 larger than those of the central\nregion. Various systematic effects, including the spatial fluctuations in the\ncosmic X-ray background, are taken into account and evaluated. These our\nresults have not changed significantly.", "category": "astro-ph_CO" }, { "text": "Average Heating Rate of Hot Atmospheres in Distant Clusters by Radio\n AGN: Evidence for Continuous AGN Heating: We examine atmospheric heating by radio active galactic nuclei (AGN) in\ndistant X-ray clusters by cross correlating clusters selected from the 400\nSquare Degree (400SD) X-ray Cluster survey with radio sources in the NRAO VLA\nSky Survey. Roughly 30% of the clusters show radio emission above a flux\nthreshold of 3 mJy within a projected radius of 250 kpc. The radio emission is\npresumably associated with the brightest cluster galaxy. The mechanical jet\npower for each radio source was determined using scaling relations between\nradio power and cavity (mechanical) power determined for nearby clusters,\ngroups, and galaxies with hot atmospheres containing X-ray cavities. The\naverage jet power of the central radio AGN is approximately $2\\times\n10^{44}$\\ergs. We find no significant correlation between radio power, hence\nmechanical jet power, and the X-ray luminosities of clusters in the redshift\nrange 0.1 -- 0.6. This implies that the mechanical heating rate per particle is\nhigher in lower mass, lower X-ray luminosity clusters. The jet power averaged\nover the sample corresponds to an atmospheric heating of approximately 0.2 keV\nper particle within R$_{500}$. Assuming the current AGN heating rate does not\nevolve but remains constant to redshifts of 2, the heating rate per particle\nwould rise by a factor of two. We find that the energy injected from radio AGN\ncontribute substantially to the excess entropy in hot atmospheres needed to\nbreak self-similarity in cluster scaling relations. The detection frequency of\nradio AGN is inconsistent with the presence of strong cooling flows in 400SD\nclusters, but does not exclude weak cooling flows. It is unclear whether\ncentral AGN in 400SD clusters are maintained by feedback at the base of a\ncooling flow. Atmospheric heating by radio AGN may retard the development of\nstrong cooling flows at early epochs.", "category": "astro-ph_CO" }, { "text": "CfA3: 185 Type Ia Supernova Light Curves from the CfA: We present multi-band photometry of 185 type-Ia supernovae (SN Ia), with over\n11500 observations. These were acquired between 2001 and 2008 at the F. L.\nWhipple Observatory of the Harvard-Smithsonian Center for Astrophysics (CfA).\nThis sample contains the largest number of homogeneously-observed and reduced\nnearby SN Ia (z < 0.08) published to date. It more than doubles the nearby\nsample, bringing SN Ia cosmology to the point where systematic uncertainties\ndominate. Our natural system photometry has a precision of 0.02 mag or better\nin BVRIr'i' and roughly 0.04 mag in U for points brighter than 17.5 mag. We\nalso estimate a systematic uncertainty of 0.03 mag in our SN Ia standard system\nBVRIr'i' photometry and 0.07 mag for U. Comparisons of our standard system\nphotometry with published SN Ia light curves and comparison stars, where\navailable for the same SN, reveal agreement at the level of a few hundredths\nmag in most cases. We find that 1991bg-like SN Ia are sufficiently distinct\nfrom other SN Ia in their color and light-curve-shape/luminosity relation that\nthey should be treated separately in light-curve/distance fitter training\nsamples. The CfA3 sample will contribute to the development of better\nlight-curve/distance fitters, particularly in the few dozen cases where\nnear-infrared photometry has been obtained and, together, can help disentangle\nhost-galaxy reddening from intrinsic supernova color, reducing the systematic\nuncertainty in SN Ia distances due to dust.", "category": "astro-ph_CO" }, { "text": "A Halo Model with Environment Dependence: Theoretical Considerations: We present a modification of the standard halo model with the goal of\nproviding an improved description of galaxy clustering. Recent surveys, like\nthe Sloan Digital Sky Survey (SDSS) and the Anglo-Australian Two-degree survey\n(2dF), have shown that there seems to be a correlation between the clustering\nof galaxies and their properties such as metallicity and star formation rate,\nwhich are believed to be environment-dependent. This environmental dependence\nis not included in the standard halo model where the host halo mass is the only\nvariable specifying galaxy properties. In our approach, the halo properties\ni.e., the concentration, and the Halo Occupation Distribution --HOD--\nprescription, will not only depend on the halo mass (like in the standard halo\nmodel) but also on the halo environment. We examine how different environmental\ndependence of halo concentration and HOD prescription affect the correlation\nfunction. We see that at the level of dark matter, the concentration of haloes\naffects moderately the dark matter correlation function only at small scales.\nHowever the galaxy correlation function is extremely sensitive to the HOD\ndetails, even when only the HOD of a small fraction of haloes is modified.", "category": "astro-ph_CO" }, { "text": "Non-Gaussianity from Isocurvature Perturbations : Analysis of\n Trispectrum: Non-Gaussianity may exist in the CDM isocurvature perturbation. We provide\ngeneral expressions for the bispectrum and trispectrum of both adiabatic and\nisocurvature pertubations. We apply our result to the QCD axion case, and found\na consistency relation between the coefficients of the bispectrum and\ntrispectrum : tau_{NL}^(iso)~10^3 [f_{NL}^(iso)]^{4/3}, if the axion is\ndominantly produced by quantum fluctuation. Thus future observations of the\ntrispectrum, as well as the bispectrum, will be important for understanding the\norigin of the CDM and baryon asymmetry.", "category": "astro-ph_CO" }, { "text": "Accretion of Galaxies around Supermassive Black Holes and a Theoretical\n Model of the Tully-Fisher and M-Sigma Relations: The observed Tully-Fisher and Faber-Jackson laws between the baryonic mass of\ngalaxies and the velocity of motion of stars at the edge of galaxies are\nexplained within the framework of the model of accretion of galaxies around\nsupermassive black holes (SMBH). The accretion model can also explain the\nM-sigma relation between the mass of a supermassive black hole and the velocity\nof stars in the bulge. The difference in the mechanisms of origin of elliptical\ngalaxies with low angular momentum and disk galaxies with high angular momentum\ncan be associated with 3D and 2D accretion.", "category": "astro-ph_CO" }, { "text": "The ability of Lisa, Taiji, and their networks to detect the stochastic\n gravitational wave background generated by Cosmic Strings: The cosmic string contributes to our understanding and revelation of the\nfundamental structure and evolutionary patterns of the universe, unifying our\nknowledge of the cosmos and unveiling new physical laws and phenomena.\nTherefore, we anticipate the detection of Stochastic Gravitational Wave\nBackground (SGWB) signals generated by cosmic strings in space-based detectors.\nWe have analyzed the detection capabilities of individual space-based\ndetectors, Lisa and Taiji, as well as the joint space-based detector network,\nLisa-Taiji, for SGWB signals produced by cosmic strings, taking into account\nother astronomical noise sources. The results indicate that the Lisa-Taiji\nnetwork exhibits superior capabilities in detecting SGWB signals generated by\ncosmic strings and can provide strong evidence. The Lisa-Taiji network can\nachieve an uncertainty estimation of $\\Delta G\\mu/G\\mu<0.5$ for cosmic string\ntension $G\\mu\\sim4\\times10^{-17}$, and can provide evidence for the presence of\nSGWB signals generated by cosmic strings at $G\\mu\\sim10^{-17}$, and strong\nevidence at $G\\mu\\sim10^{-16}$. Even in the presence of only SGWB signals, it\ncan achieve a relative uncertainty of $\\Delta G\\mu/G\\mu<0.5$ for cosmic string\ntension $G\\mu<10^{-18}$, and provide strong evidence at $G\\mu\\sim10^{-17}$.", "category": "astro-ph_CO" }, { "text": "An analytical approximation of the luminosity distance in flat\n cosmologies with a cosmological constant: We present an analytical approximation formula for the luminosity distance in\nspatially flat cosmologies with dust and a cosmological constant. Apart from\nthe overall factor, the effect of non-zero cosmological constant in our formula\nis written simply in terms of a rational function. We also show the approximate\nformulae for the Dyer-Roeder distance (empty beam case) and the generalized\nangular diameter distance from redshift $z_1$ to $z_2$, which are particularly\nuseful in analyzing the gravitational lens effects. Our formulae are widely\napplicable over the range of the density parameter and the redshift with\nsufficiently small uncertainties. In particular, in the range of density\nparameter $0.3 \\leq \\Omega_{\\rm m} \\leq 1$ and redshift $0.03 \\leq z \\leq\n1000$, the relative error for the luminosity distance by our formula is always\nsmaller than that of the recent work by Wickramasinghe and Ukwatta (2010).\nHence, we hope that our formulae will be an efficient and useful tool for\nexploring various problems in observational cosmology.", "category": "astro-ph_CO" }, { "text": "Weak Lensing Measurements in Simulations of Radio Images: We present a study of weak lensing shear measurements for simulated galaxy\nimages at radio wavelengths. We construct a simulation pipeline into which we\ncan input galaxy images of known ellipticity, and with which we then simulate\nobservations with eMERLIN and the international LOFAR array. The simulations\ninclude the effects of the CLEAN algorithm, uv sampling, observing angle, and\nvisibility noise, and produce realistic restored images of the galaxies. We\napply a shapelet-based shear measurement method to these images and test our\nability to recover the true source ellipticities. We model and deconvolve the\neffective PSF, and find suitable parameters for CLEAN and shapelet\ndecomposition of galaxies. We demonstrate that ellipticities can be measured\nfaithfully in these radio simulations, with no evidence of an additive bias and\na modest (10%) multiplicative bias on the ellipticity measurements. Our\nsimulation pipeline can be used to test shear measurement procedures and\nsystematics for the next generation of radio telescopes.", "category": "astro-ph_CO" }, { "text": "A Universe without Dark Energy and Dark Matter: The universe has evolved to be a filamentary web of galaxies and large\ninter-galactic zones of space without matter. The Euclidian nature of the\nuniverse indicates that it is not a 3D manifold within space with an extra\nspatial dimension. This justifies our assumption that the FRW space-time\nevolves in the inter-galactic zones like separate FRW universes. Thus we do not\nnecessarily have to consider the entirety of the universe. Our assumption\nenables us to prove that: -In the current epoch, space in the intergalactic\nzones expands at a constant rate. -In and around galaxies, space expansion is\ninhibited. With these results, and an extended Gauss Theorem for a deformed\nspace, we show that there is no need for the hypothetical Dark Energy (DE) and\nDark Matter (DM) to explain phenomena attributed to them.", "category": "astro-ph_CO" }, { "text": "Searching for spin-2 ULDM with gravitational waves interferometers: The detection of gravitational waves from merging binaries has ushered in the\nera of gravitational wave interferometer astronomy. Besides these strong,\ntransient, calamitous events, much weaker signals can be detected if the\noscillations are nearly monochromatic and \"continuous\", that is, coherent over\na long time. In this work we show that ultra-light dark matter of spin two,\nowing to its universal coupling $\\alpha$ to Standard Model fields, generates a\nsignal that is akin to but distinct from a continuous gravitational wave. We\nshow that this signal could be detected with current and planned gravitational\nwave interferometers. In the event of a null detection, current facilities\ncould constrain the coupling to be below $\\alpha\\sim10^{-7}$ for frequencies of\ntens of Hz, corresponding to dark matter masses around the $10^{-13}$ eV mark.\nFuture facilities could further lower these upper limits and extend them to\nsmaller masses down to $10^{-18}$ eV. These limits would be the most stringent\nbounds on the spin-2 Yukawa fifth force strength, parametrised by $\\alpha$, in\nthe frequency ranges accessible by gravitational wave interferometers. The\nimplementation of this type of searches for gravitational wave interferometers\nwould therefore further our grasp of both dark matter and gravity.", "category": "astro-ph_CO" }, { "text": "Constraints on a mixed model of dark matter particles and primordial\n black holes from the Galactic 511 keV line: The galactic 511 keV gamma-ray line has been observed since 1970's, and was\nidentified as the result of electron-positron annihilation, but the origin of\nsuch positrons is still not clear. Apart from the astrophysical explanations,\nthe possibilities that such positrons come from dark matter (DM) annihilation\nare also widely studied. Primordial black hole (PBH) is also an extensively\nstudied candidate of DM. If PBHs exist, the DM particles may be gravitationally\nbound to the PBHs and form halo around PBHs with density spikes. DM\nannihilation in these density spikes can enhance the production rate of\npositrons from DM particles, but the signal morphology is similar to the\ndecaying DM. We consider such a mixed model consisting of DM particles and PBHs\nand obtain the upper limit from the data of 511 keV gamma-ray line from\nINTEGRAL/SPI on the decaying component of DM particles and the constraint on\nthe PBH abundance. These constraints are general and independent of particle DM\nmodels. For the mixed model consisting of excited DM and PBHs, the constraints\non the PBH abundance can be down to $O(10^{-17})$ for DM particle with mass\naround $1~\\mathrm{TeV}$, which is more stringent than that obtained from the\nextragalactic gamma-ray background.", "category": "astro-ph_CO" }, { "text": "The Carnegie Supernova Project: Light Curve Fitting with SNooPy: In providing an independent measure of the expansion history of the Universe,\nthe Carnegie Supernova Project (CSP) has observed 71 high-z Type Ia supernovae\n(SNe Ia) in the near-infrared bands Y and J. These can be used to construct\nrest-frame i-band light curves which, when compared to a low-z sample, yield\ndistance moduli that are less sensitive to extinction and/or decline-rate\ncorrections than in the optical. However, working with NIR observed and i-band\nrest frame photometry presents unique challenges and has necessitated the\ndevelopment of a new set of observational tools in order to reduce and analyze\nboth the low-z and high-z CSP sample. We present in this paper the methods used\nto generate uBVgriYJH light-curve templates based on a sample of 24\nhigh-quality low-z CSP SNe. We also present two methods for determining the\ndistances to the hosts of SN Ia events. A larger sample of 30 low-z SNe Ia in\nthe Hubble Flow are used to calibrate these methods. We then apply the method\nand derive distances to seven galaxies that are so nearby that their motions\nare not dominated by the Hubble flow.", "category": "astro-ph_CO" }, { "text": "Star formation in galaxy interactions and mergers: This lecture reviews the fundamental physical processes involved in star\nformation in galaxy interactions and mergers. Interactions and mergers often\ndrive intense starbursts, but the link between interstellar gas physics, large\nscale interactions, and active star formation is complex and not fully\nunderstood yet. Two processes can drive starbursts: radial inflows of gas can\nfuel nuclear starbursts, triggered gas turbulence and fragmentation can drive\nmore extended starbursts in massive star clusters with high fractions of dense\ngas. Both modes are certainly required to account for the observed properties\nof starbursting mergers. A particular consequence is that star formation\nscaling laws are not universal, but vary from quiescent disks to starbursting\nmergers. High-resolution hydrodynamic simulations are used to illustrate the\nlectures.", "category": "astro-ph_CO" }, { "text": "Exploring 21cm - Lyman Alpha emitter synergies for SKA: We study the signatures of reionization and ionizing properties of the early\ngalaxies in the cross-correlations between the 21cm emission from the spin-flip\ntransition of neutral hydrogen (HI) and the underlying galaxy population, in\nparticular a sub-population of galaxies visible as Lyman Alpha Emitters (LAEs).\nWith both observables simultaneously derived from a $z\\simeq6.6$ hydrodynamical\nsimulation (GADGET-2) snapshot post-processed with a radiative transfer code\n(pCRASH) and a dust model, we perform a parameter study and aim to constrain\nboth the average intergalactic medium (IGM) ionization state ($1-\\langle\n\\chi_{HI} \\rangle$) and the reionization topology (outside-in versus\ninside-out). We find that in our model LAEs occupy the densest and most-ionized\nregions resulting in a very strong anti-correlation between the LAEs and the\n21cm emission. A 1000h SKA-LOW1 - Subaru Hyper Suprime Cam experiment can\nprovide constraints on $\\langle \\chi_{HI} \\rangle$, allowing us to distinguish\nbetween IGM ionization levels of 50%, 25%, 10% and fully ionized at scales\n$r<10$ comoving Mpc (assuming foreground avoidance for SKA). Our results\nsupport the inside-out reionization scenario where the densest knots\n(under-dense voids) are ionized first (last) for $\\langle \\chi_{HI} \\rangle >=\n0.1$. Further, 1000h SKA-LOW1 observations should be able to confirm the\ninside-out scenario by detecting a lower 21cm brightness temperature (by about\n2-10 mK) in the densest regions ($> 2$ arcminute scales) hosting LAEs compared\nto lower-density regions devoid of them.", "category": "astro-ph_CO" }, { "text": "Dark energy in light of the early JWST observations: case for a negative\n cosmological constant?: Early data from the James Webb Space Telescope (JWST) has uncovered the\nexistence of a surprisingly abundant population of very massive galaxies at\nextremely high redshift, which are hard to accommodate within the standard\n$\\Lambda$CDM cosmology. We explore whether the JWST observations may be\npointing towards more complex dynamics in the dark energy (DE) sector.\nMotivated by the ubiquity of anti-de Sitter vacua in string theory, we consider\na string-inspired scenario where the DE sector consists of a negative\ncosmological constant (nCC) and a evolving component with positive energy\ndensity on top, whose equation of state is allowed to cross the phantom divide.\nWe show that such a scenario can drastically alter the growth of structure\ncompared to $\\Lambda$CDM, and accommodate the otherwise puzzling JWST\nobservations if the dynamical component evolves from the quintessence-like\nregime in the past to the phantom regime today: in particular, we demonstrate\nthat the presence of a nCC (which requires a higher density for the evolving\ncomponent) plays a crucial role in enhancing the predicted cumulative comoving\nstellar mass density. Our work reinforces the enormous potential held by\nobservations of the abundance of high-$z$ galaxies in probing cosmological\nmodels and new fundamental physics, including string-inspired ingredients.", "category": "astro-ph_CO" }, { "text": "Curvaton preheating revisited: We study the thermalization process in the self-interacting curvaton\npreheating scenario. We solve the evolution of the system with classical\nlattice simulations with a recently released symplectic PyCOOL program during\nthe resonance and the early thermalization periods and compare the results to\nthe inflaton preheating. After this we calculate the generated non-gaussianity\nwith the $\\Delta N$ formalism and the separate universe approximation by\nrunning a large number of simulations with slightly different initial values.\nThe results indicate a high level of non-gaussianity. We also use this paper to\nshowcase the various post-processing functions included with the PyCOOL program\nthat is available from https://github.com/jtksai/PyCOOL .", "category": "astro-ph_CO" }, { "text": "Simulation-based inference of dynamical galaxy cluster masses with 3D\n convolutional neural networks: We present a simulation-based inference framework using a convolutional\nneural network to infer dynamical masses of galaxy clusters from their observed\n3D projected phase-space distribution, which consists of the projected galaxy\npositions in the sky and their line-of-sight velocities. By formulating the\nmass estimation problem within this simulation-based inference framework, we\nare able to quantify the uncertainties on the inferred masses in a\nstraightforward and robust way. We generate a realistic mock catalogue\nemulating the Sloan Digital Sky Survey (SDSS) Legacy spectroscopic observations\n(the main galaxy sample) for redshifts $z \\lesssim 0.09$ and explicitly\nillustrate the challenges posed by interloper (non-member) galaxies for cluster\nmass estimation from actual observations. Our approach constitutes the first\noptimal machine learning-based exploitation of the information content of the\nfull 3D projected phase-space distribution, including both the virialized and\ninfall cluster regions, for the inference of dynamical cluster masses. We also\npresent, for the first time, the application of a simulation-based inference\nmachinery to obtain dynamical masses of around $800$ galaxy clusters found in\nthe SDSS Legacy Survey, and show that the resulting mass estimates are\nconsistent with mass measurements from the literature.", "category": "astro-ph_CO" }, { "text": "Lagrangian bias of generic large-scale structure tracers: The dark matter halos that host galaxies and clusters form out of initial\nhigh-density patches, providing a biased tracer of the linear matter density\nfield. In the simplest local bias approximation, the halo field is treated as a\nperturbative series in the average overdensity of the Lagrangian patch. In more\nrealistic models, however, additional quantities will affect the clustering of\nhalo-patches, and this expansion becomes a function of several stochastic\nvariables. In this paper, we present a general multivariate expansion scheme\nthat can parametrize the clustering of any biased Lagrangian tracer, given only\nthe variables involved and their symmetry (in our case rotational invariance).\nThis approach is based on an expansion in the orthonormal polynomials\nassociated with the relevant variables, so that no renormalization of the\ncoefficients ever occurs. We provide explicit expression for the series\ncoefficients, or Lagrangian bias parameters, in the case of peaks of the linear\ndensity field. As an application of our formalism, we present a simple\nderivation of the original BBKS formula, and compute the non-Gaussian bias in\nthe presence of a primordial trispectrum of the local shape.", "category": "astro-ph_CO" }, { "text": "The growth of density perturbations in the last $\\sim$10 billion years\n from tomographic large-scale structure data: In order to investigate the origin of the ongoing tension between the\namplitude of matter fluctuations measured by weak lensing experiments at low\nredshifts and the value inferred from the cosmic microwave background\nanisotropies, we reconstruct the evolution of this amplitude from $z\\sim2$\nusing existing large-scale structure data. To do so, we decouple the linear\ngrowth of density inhomogeneities from the background expansion, and constrain\nits redshift dependence making use of a combination of 6 different data sets,\nincluding cosmic shear, galaxy clustering and CMB lensing. We analyze these\ndata under a consistent harmonic-space angular power spectrum-based pipeline.\nWe show that current data constrain the amplitude of fluctuations mostly in the\nrange $0.2 10E44 erg/s) is significantly\nflatter than the average for the lower luminosity sources. We also find that\nthe intrinsic column density distribution agrees with AGN unified schemes,\nalthough a number of exceptions are found (3% of the whole sample), which are\nmuch more common among optically classified type 2 AGN. We also find that the\nso-called \"soft-excess\", apart from the intrinsic absorption, constitutes the\nprincipal deviation from a power-law shape in AGN X-ray spectra and it clearly\ndisplays different characteristics, and likely a different origin, for\nunabsorbed and absorbed AGN. Regarding the shape of the average spectra, we\nfind that it is best reproduced by a combination of an unabsorbed (absorbed)\npower law, a narrow Fe Kalpha emission line and a small (large) amount of\nreflection for unabsorbed (absorbed) sources. We do not significantly detect\nany relativistic contribution to the line emission and we compute an upper\nlimit for its equivalent width (EW) of 230 eV at the 3 sigma confidence level.\nFinally, by dividing the type 1 AGN sample into high- and low-luminosity\nsources, we marginally detect a decrease in the narrow Fe Kalpha line EW and in\nthe amount of reflection as the luminosity increases, the \"so-called\"\nIwasawa-Taniguchi effect.", "category": "astro-ph_CO" }, { "text": "Statistical anisotropy of CMB as a probe of conformal rolling scenario: Search for the statistical anisotropy in the CMB data is a powerful tool for\nconstraining models of the early Universe. In this paper we focus on the\nrecently proposed cosmological scenario with conformal rolling. We consider two\nsub-scenarios, one of which involves a long intermediate stage between\nconformal rolling and conventional hot epoch. Primordial scalar perturbations\ngenerated within these sub-scenarios have different direction-dependent power\nspectra, both characterized by a single parameter h^2. We search for the\nsignatures of this anisotropy in the seven-year WMAP data using quadratic\nmaximum likelihood method, first applied for similar purposes by Hanson and\nLewis. We confirm the large quadrupole anisotropy detected in V and W bands,\nwhich has been argued to originate from systematic effects rather than from\ncosmology. We construct an estimator for the parameter h^2. In the case of the\nsub-scenario with the intermediate stage we set an upper limit h^2 < 0.045 at\nthe 95% confidence level. The constraint on h^2 is much weaker in the case of\nanother sub-scenario, where the intermediate stage is absent.", "category": "astro-ph_CO" }, { "text": "Polar Ring Galaxies in the Galaxy Zoo: We report observations of 16 candidate polar ring galaxies (PRGs) identified\nby the Galaxy Zoo project in the Sloan Digital Sky Survey (SDSS) database. Deep\nimages of five galaxies are available in the SDSS Stripe82 database, while to\nreach similar depth we observed the remaining galaxies with the 1.8-m Vatican\nAdvanced Technology Telescope. We derive integrated magnitudes and u-r colours\nfor the host and ring components and show continuum-subtracted H\\alpha+[NII]\nimages for seven objects. We present a basic morphological and environmental\nanalysis of the galaxies and discuss their properties in comparison with other\ntypes of early-type galaxies. Follow-up photometric and spectroscopic\nobservations will allow a kinematic confirmation of the nature of these systems\nand a more detailed analysis of their stellar populations.", "category": "astro-ph_CO" }, { "text": "Constraining Dust and Molecular Gas Properties in Lyman Alpha Blobs at\n z~3: In order to constrain the bolometric luminosities, dust properties and\nmolecular gas content of giant Lyman alpha nebulae, the so-called Lyman alpha\nblobs, we have carried out a study of dust continuum and CO line emission in\ntwo well-studied representatives of this population at z ~ 3: a Lya blob\ndiscovered by its strong Spitzer MIPS 24um detection (LABd05; Dey et al. 2005)\nand the Steidel blob 1 (SSA22-LAB01; Steidel et al. 2000). We find that the\nspectral energy distribution of LABd05 is well described by an AGN-starburst\ncomposite template with L(FIR) = (4.0 +/- 0.5) x 10^12 Lsun, comparable to\nhigh-z sub-millimeter galaxies and ultraluminous infrared galaxies. New\nAPEX/LABOCA 870um measurements rule out the reported SCUBA detection of the\nSSA22-LAB01 (S[850um] = 16.8 mJy) at the > 4sigma level. Consistent with this,\nultra-deep Plateau de Bure Interferometer (PdBI) observations with ~2arcsec\nspatial resolution also fail to detect any 1.2mm continuum source down to\n~0.45mJy per beam (3sigma). Combined with the existing (sub)mm observations in\nthe literature, we conclude that the FIR luminosity of SSA22-LAB01 remains\nuncertain. No CO line is detected in either case down to integrated flux limits\nof (Snu dV) < 0.25--1.0 Jy km/s, indicating a modest molecular gas reservoir,\nM(H_2) < 1--3 x 10^10 Msun. The non-detections exclude, with high significance\n(12 sigma), the previous tentative detection of a CO(4-3) line in the\nSSA22-LAB01. The increased sensitivity afforded by ALMA will be critical in\nstudying molecular gas and dust in these interesting systems.", "category": "astro-ph_CO" }, { "text": "Effects of boosting on extragalactic components: methods and statistical\n studies: In this work we examine the impact of our motion with respect to the CMB rest\nframe on statistics of CMB maps by examining the one-, two-, three- and four-\npoint statistics of simulated maps of the CMB and Sunyaev-Zeldovich (SZ)\neffects. We validate boosting codes by comparing their outcomes for temperature\nand polarization power spectra up to $\\ell \\simeq 6000$. We derive and validate\na new analytical formula for the computation of the boosted power spectrum of a\nsignal with a generic frequency dependence. As an example we show how this\nincreases the boosting correction to the power spectrum of CMB intensity\nmeasurements by $\\sim 30\\%$ at 150 GHz. We examine the effect of boosting on\nthermal and kinetic SZ power spectra from semianalytical and hydrodynamical\nsimulations; the boosting correction is generally small for both simulations,\nexcept when considering frequencies near the tSZ null. For the non-Gaussian\nstatistics, in general we find that boosting has no impact with two exceptions.\nWe find that, whilst the statistics of the CMB convergence field are\nunaffected, quadratic estimators that are used to measure this field can become\nbiased at the $O(1)\\%$ level by boosting effects. We present a simple\nmodification to the standard estimators that removes this bias. Second,\nbispectrum estimators can receive a systematic bias from the Doppler induced\nquadrupole when there is anisotropy in the sky -- in practice this anisotropy\ncomes from masking and inhomogenous noise. This effect is unobservable and\nalready removed by existing analysis methods.", "category": "astro-ph_CO" }, { "text": "Non-Gaussian Scatter in Cluster Scaling Relations: We investigate the impact of non-Gaussian scatter in the cluster\nmass-observable scaling relation on the mass and redshift distribution of\nclusters detected by wide area surveys. We parameterize non-Gaussian scatter by\nincorporating the third and forth moments (skewness and kurtosis) into the\ndistribution P(Mobs|M). We demonstrate that for low scatter mass proxies the\nhigher order moments do not significantly affect the observed cluster mass and\nredshift distributions. However, for high scatter mass indicators it is\nnecessary for the survey limiting mass threshold to be less than 10^14 h^-1\nMsol to prevent the skewness from having a significant impact on the observed\nnumber counts, particularly at high redshift. We also show that an unknown\nlevel of non-Gaussianity in the scatter is equivalent to an additional\nuncertainty on the variance in P(Mobs|M) and thus may limit the constraints\nthat can be placed on the dark energy equation of state parameter w.\nFurthermore, positive skewness flattens the mass function at the high mass end,\nand so one must also account for skewness in P(Mobs|M) when using the shape of\nthe mass function to constrain cluster scaling-relations.", "category": "astro-ph_CO" }, { "text": "A new probe of Axion-Like Particles: CMB polarization distortions due to\n cluster magnetic fields: We propose using the upcoming Cosmic Microwave Background (CMB) ground based\nexperiments to detect the signal of ALPs (Axion like particles) interacting\nwith magnetic fields in galaxy clusters. The conversion between CMB photons and\nALPs in the presence of the cluster magnetic field can cause a polarized\nspectral distortion in the CMB around a galaxy cluster. The strength of the\nsignal depends upon the redshift of the galaxy cluster and will exhibit a\ndistinctive spatial profile around it depending upon the structure of electron\ndensity and magnetic field. This distortion produces a different shape from the\nother known spectral distortions like $y$-type and $\\mu$-type and hence are\nseparable from the multi-frequency CMB observation. The spectrum is close to\nkinematic Sunyaev-Zeldovich (kSZ) signal but can be separated from it using the\npolarization information. For the future ground-based CMB experiments such as\nSimons Observatory and CMB-S4, we estimate the measurability of this signal in\nthe presence of foreground contamination, instrument noise and CMB\nanisotropies. This new avenue can probe the photon-ALP coupling over the ALP\nmass range from $10^{-13}$ eV to $10^{-12}$ eV with two orders of magnitude\nbetter accuracy from CMB-S4 than the current existing bounds.", "category": "astro-ph_CO" }, { "text": "Bayesian inferences of galaxy formation from the K-band luminosity and\n HI mass functions of galaxies: constraining star formation and feedback: We infer mechanisms of galaxy formation for a broad family of semi-analytic\nmodels (SAMs) constrained by the K-band luminosity function and HI mass\nfunction of local galaxies using tools of Bayesian analysis. Even with a broad\nsearch in parameter space the whole model family fails to match to constraining\ndata. In the best fitting models, the star formation and feedback parameters in\nlow-mass haloes are tightly constrained by the two data sets, and the analysis\nreveals several generic failures of models that similarly apply to other\nexisting SAMs. First, based on the assumption that baryon accretion follows the\ndark matter accretion, large mass-loading factors are required for haloes with\ncircular velocities lower than 200 km/s, and most of the wind mass must be\nexpelled from the haloes. Second, assuming that the feedback is powered by\nType-II supernovae with a Chabrier IMF, the outflow requires more than 25% of\nthe available SN kinetic energy. Finally, the posterior predictive\ndistributions for the star formation history are dramatically inconsistent with\nobservations for masses similar to or smaller than the Milky-Way mass. The\ninferences suggest that the current model family is still missing some key\nphysical processes that regulate the gas accretion and star formation in\ngalaxies with masses below that of the Milky Way.", "category": "astro-ph_CO" }, { "text": "The background Friedmannian Hubble constant in relativistic\n inhomogeneous cosmology and the age of the Universe: In relativistic inhomogeneous cosmology, structure formation couples to\naverage cosmological expansion. A conservative approach to modelling this\nassumes an Einstein--de Sitter model (EdS) at early times and extrapolates this\nforward in cosmological time as a \"background model\" against which average\nproperties of today's Universe can be measured. This requires adopting an\nearly-epoch--normalised background Hubble constant $H_1^{bg}$. Here, we show\nthat the $\\Lambda$CDM model can be used as an observational proxy to estimate\n$H_1^{bg}$ rather than choose it arbitrarily. We assume (i) an EdS model at\nearly times; (ii) a zero dark energy parameter; (iii) bi-domain scalar\naveraging---division of the spatial sections into over- and underdense regions;\nand (iv) virialisation (stable clustering) of collapsed regions. We find\n$H_1^{bg}= 37.7 \\pm 0.4$ km/s/Mpc (random error only) based on a Planck\n$\\Lambda$CDM observational proxy. Moreover, since the scalar-averaged expansion\nrate is expected to exceed the (extrapolated) background expansion rate, the\nexpected age of the Universe should be much less than $2/(3 H_1^{bg}) = 17.3$\nGyr. The maximum stellar age of Galactic Bulge microlensed low-mass stars (most\nlikely: 14.7 Gyr; 68\\% confidence: 14.0--15.0 Gyr) suggests an age about a Gyr\nolder than the (no-backreaction) $\\Lambda$CDM estimate.", "category": "astro-ph_CO" }, { "text": "Relativistic static magnetized finite thin disk: An infinite family of\n exact solutions: An infinite family of relativistic finite thin disk model with magnetic field\nis presented. The model is obtained for solving the Einstein-Maxwell equations\nfor static spacetimes by means of the Horsk\\'y-Mitskievitch generating\nconjecture. The vacuum limit of these obtained solutions is the well known\nMorgan and Morgan solution. The obtained expressions are simply written in\nterms of oblate spheroidal coordinates. The mass of the disks are finite and\nthe energy-momentum tensor agrees with all the energy conditions. The magnetic\nfield and the circular velocity are evaluated explicitly. All the physical\nquantities obtained shown an acceptable", "category": "astro-ph_CO" }, { "text": "The evolution of dusty torus covering factor in quasars: We have assembled a large sample of 5996 quasars at redshift 2.0=< z <= 2.4\n(high-z) or 0.7=< z <= 1.1 (low-z) from SDSS data release nine and seven quasar\ncatalogs. The spectral energy distribution (SED) of quasars were constructed by\ncollecting WISE, UKIDSS, and GALEX photometric data in addition to SDSS, from\nwhich the IR luminosity at 1-7 \\mu m and bolometric luminosity at 1100 \\AA - 1\n\\mu m were calculated. A red tail is clearly seen in the distributions of the\nspectral index in 1100 \\AA - 1 \\mu m both for high-z and low-z sources, which\nis likely due to red or reddened quasars. The covering factor of dusty torus is\nestimated as the ratio of the IR luminosity to the bolometric luminosity. We\nfound significant anti-correlations between the covering factor and bolometric\nluminosity, in both high-z and low-z quasars, however they follow different\ntracks. At overlapped bolometric luminosity, the covering factor of high-z\nquasars are systematically larger than those of low-z quasars, implying an\nevolution of covering factor with redshift.", "category": "astro-ph_CO" }, { "text": "On the tension between growth rate and CMB data: We analyze the claimed tension between redshift space distorsions\nmeasurements of $f(z)\\sigma_8(z)$ and the predictions of standard $\\Lambda$CDM\n(Planck 2015 and 2018) cosmology. We consider a dataset consisting of 17 data\npoints extending up to redshift $z=1.52$ and corrected for the Alcock-Paczynski\neffect. Thus, calculating the evolution of the growth factor in a $w$CDM\ncosmology, we find that the tension for the best fit parameters $w$, $\\Omega_m$\nand $\\sigma_8$ with respect to the Planck 2018 $\\Lambda$CDM parameters is below\n$2\\sigma$ in all the marginalized confidence regions.", "category": "astro-ph_CO" }, { "text": "Detection of Cosmic Magnification via Galaxy Shear -- Galaxy Number\n Density Correlation from HSC Survey Data: We propose a novel method to detect cosmic magnification signals by\ncross-correlating foreground convergence fields constructed from galaxy shear\nmeasurements with background galaxy positional distributions, namely\nshear-number density correlation. We apply it to the Hyper Suprime-Cam Subaru\nStrategic Program (HSC-SSP) survey data. With 27 non-independent data points\nand their full covariance, $\\chi_0^2\\approx 34.1$ and $\\chi_T^2\\approx 24.0$\nwith respect to the null and the cosmological model with the parameters from\nHSC shear correlation analyses in Hamana et al. 2020 (arXiv:1906.06041),\nrespectively. The Bayes factor of the two is $\\log_{10}B_{T0}\\approx 2.2$\nassuming equal model probabilities of null and HSC cosmology, showing a clear\ndetection of the magnification signals. Theoretically, the ratio of the\nshear-number density and shear-shear correlations can provide a constraint on\nthe effective multiplicative shear bias $\\bar m$ using internal data\nthemselves. We demonstrate the idea with the signals from our HSC-SSP mock\nsimulations and rescaling the statistical uncertainties to a survey of\n$15000\\deg^2$. For two-bin analyses with background galaxies brighter than\n$m_{lim}=23$, the combined analyses lead to a forecasted constraint of\n$\\sigma(\\bar m) \\sim 0.032$, $2.3$ times tighter than that of using the\nshear-shear correlation alone. Correspondingly, $\\sigma(S_8)$ with\n$S_8=\\sigma_8(\\Omega_\\mathrm{m}/0.3)^{0.5}$ is tightened by $\\sim 2.1$ times.\nImportantly, the joint constraint on $\\bar m$ is nearly independent of\ncosmological parameters. Our studies therefore point to the importance of\nincluding the shear-number density correlation in weak lensing analyses, which\ncan provide valuable consistency tests of observational data, and thus to\nsolidify the derived cosmological constraints.", "category": "astro-ph_CO" }, { "text": "H0 Revisited: I reanalyse the Riess et al. (2011, hereafter R11) Cepheid data using the\nrevised geometric maser distance to NGC 4258 of Humphreys et al. (2013). I\nexplore different outlier rejection criteria designed to give a reduced\nchi-squared of unity and compare the results with the R11 rejection algorithm,\nwhich produces a reduced chi-squared that is substantially less than unity and,\nin some cases, to underestimates of the errors on parameters. I show that there\nare sub-luminous low metallicity Cepheids in the R11 sample that skew the\nglobal fits of the period-luminosity relation. This has a small but\nnon-negligible impact on the global fits using NGC 4258 as a distance scale\nanchor, but adds a poorly constrained source of systematic error when using the\nLarge Magellanic Cloud (LMC) as an anchor. I also show that the small Milky Way\n(MW) Cepheid sample with accurate parallax measurements leads to a distance to\nNGC 4258 that is in tension with the maser distance. I conclude that H0 based\non the NGC 4258 maser distance is H0 = 70.6 +/- 3.3 km/s/Mpc compatible within\n1 sigma with the recent determination from Planck for the base six-parameter\nLCDM cosmology. If the H-band period-luminosity relation is assumed to be\nindependent of metallicity and the three distance anchors are combined, I find\nH0 = 72.5 +/- 2.5 km/s/Mpc, which differs by 1.9 sigma from the Planck value.\nThe differences between the Planck results and these estimates of H0 are not\nlarge enough to provide compelling evidence for new physics at this stage.", "category": "astro-ph_CO" }, { "text": "Growth of matter perturbations in the extended viscous dark energy\n models: In this work, we study the extended viscous dark energy models in the context\nof matter perturbations. To do this, we assume an alternative interpretation of\nthe flat Friedmann-Lema\\^itre-Robertson-Walker Universe, through the\nnonadditive entropy and the viscous dark energy. We implement the relativistic\nequations to obtain the growth of matter fluctuations for a smooth version of\ndark energy. As result, we show that the matter density contrast evolves\nsimilarly to the $\\Lambda$CDM model in high redshift; in late time, it is\nslightly different from the standard model. Using the latest geometrical and\ngrowth rate observational data, we carry out a Bayesian analysis to constrain\nparameters and compare models. We see that our viscous models are compatible\nwith cosmological probes, and the $\\Lambda$CDM recovered with a $1\\sigma$\nconfidence level. The viscous dark energy models relieve the tension of $H_0$\nin $2 \\sim 3 \\sigma$. Yet, by involving the $\\sigma_8$ tension, some models can\nalleviate it. In the model selection framework, the data discards the extended\nviscous dark energy models.", "category": "astro-ph_CO" }, { "text": "SDSS superclusters: morphology and galaxy content: We compare the galaxy populations in superclusters of different morphology in\nthe nearby Universe (180 < d < 270 Mpc) to see whether the inner structure and\noverall morphology of superclusters are important in shaping galaxy properties\nin superclusters. Supercluster morphology has been found with Minkowski\nfunctionals. We analyse the probability density distributions of colours,\nmorphological types, stellar masses, star formation rates (SFR) of galaxies,\nand the peculiar velocities of the main galaxies in groups in superclusters of\nfilament and spider types, and in the field. We show that the fraction of red,\nearly-type, low SFR galaxies in filament-type superclusters is higher than in\nspider-type superclusters; in low-density global environments their fraction is\nlower than in superclusters. In all environments the fraction of red, high\nstellar mass, and low SFR galaxies in rich groups is higher than in poor\ngroups. In superclusters of spider morphology red, high SFR galaxies have\nhigher stellar masses than in filament-type superclusters. Groups of equal\nrichness host galaxies with larger stellar masses, a larger fraction of\nearly-type and red galaxies, and a higher fraction of low SFR galaxies, if they\nare located in superclusters of filament morphology. The peculiar velocities of\nthe main galaxies in groups from superclusters of filament morphology are\nhigher than in those of spider morphology. Groups with higher peculiar\nvelocities of their main galaxies in filament-type superclusters are located in\nhigher density environment than those with low peculiar velocities. There are\nsignificant differences between galaxy populations of the individual richest\nsuperclusters. Therefore both local (group) and global (supercluster)\nenvironments and even supercluster morphology play an important role in the\nformation and evolution of galaxies.", "category": "astro-ph_CO" }, { "text": "The state of the dark energy equation of state circa 2023: We critically examine the state of current constraints on the dark energy\n(DE) equation of state (EoS) $w$. Our study is partially motivated by the\nobservation that, while broadly consistent with the cosmological constant value\n$w=-1$, several independent probes appear to point towards a slightly phantom\nEoS ($w \\sim -1.03$). We pay attention to the apparent preference for phantom\nDE from Planck Cosmic Microwave Background (CMB) data alone, whose origin we\nstudy in detail and attribute to a wide range of (physical and geometrical)\neffects. We deem the combination of Planck CMB, Baryon Acoustic Oscillations,\nType Ia Supernovae, and Cosmic Chronometers data to be particularly\ntrustworthy, inferring from this final consensus dataset\n$w=-1.013^{+0.038}_{-0.043}$, in excellent agreement with the cosmological\nconstant value. Overall, despite a few scattered hints, we find no compelling\nevidence forcing us away from the cosmological constant (yet).", "category": "astro-ph_CO" }, { "text": "The supermassive black hole mass - S\u00e9rsic index relations for bulges\n and elliptical galaxies: Scaling relations between supermassive black hole mass, M_BH, and host galaxy\nproperties are a powerful instrument for studying their coevolution. A complete\npicture involving all of the black hole scaling relations, in which each\nrelation is consistent with the others, is necessary to fully understand the\nblack hole-galaxy connection. The relation between M_BH and the central light\nconcentration of the surrounding bulge, quantified by the S\\'ersic index n, may\nbe one of the simplest and strongest such relations, requiring only\nuncalibrated galaxy images. We have conducted a census of literature S\\'ersic\nindex measurements for a sample of 54 local galaxies with directly measured\nM_BH values. We find a clear M_BH - n relation, despite an appreciable level of\nscatter due to the heterogeneity of the data. Given the current M_BH - L_sph\nand the L_sph - n relations, we have additionally derived the expected M_BH - n\nrelations, which are marginally consistent at the 2 sigma level with the\nobserved relations. Elliptical galaxies and the bulges of disc galaxies are\neach expected to follow two distinct bent M_BH - n relations due to the\nS\\'ersic/core-S\\'ersic divide. For the same central light concentration, we\npredict that M_BH in the S\\'ersic bulges of disc galaxies are an order\nmagnitude higher than in S\\'ersic elliptical galaxies if they follow the same\nM_BH - L_sph relation.", "category": "astro-ph_CO" }, { "text": "Gas and dark matter in the Sculptor group: NGC 55: We present new, sensitive HI observations of the Sculptor group galaxy NGC 55\nwith the Australia Telescope Compact Array. We achieve a 5 sigma HI column\ndensity sensitivity of 10^19 cm^-2 over a spectral channel width of 8 km/s for\nemission filling the 158\" x 84\" synthesised beam. Our observations reveal for\nthe first time the full extent of the HI disc of NGC 55 at this sensitivity and\nat a moderately high spatial resolution of about 1 kpc.\n The HI disc of NGC 55 appears to be distorted on all scales. There is a\nstrong east-west asymmetry in the column density distribution along the major\naxis, suggesting that the disc is under the influence of ram-pressure forces.\nWe also find evidence of streaming motions of the gas along the bar of NGC 55.\nThe fitting of tilted rings to the velocity field reveals a strong warping of\nthe outer gas disc which could be the result of tidal interaction with either\nNGC 300 or a smaller satellite galaxy. Finally, we find a large number of\ndistinct clumps and spurs across the entire disc, indicating that internal or\nexternal processes, such as satellite accretion or gas outflows, have stirred\nup the gas disc.\n We also detect several isolated HI clouds within about 20 kpc projected\ndistance from NGC 55. Their dynamical properties and apparent concentration\naround NGC 55 suggest that most of the clouds are forming a circum-galactic\npopulation similar to the high-velocity clouds of the Milky Way and M31,\nalthough two of the clouds could be foreground objects and part of the\nMagellanic Stream. While it is difficult to determine the origin of these\nclouds, our data seem to favour either tidal stripping or gas outflows as the\nsource of the gas.", "category": "astro-ph_CO" }, { "text": "ALFALFA HI Data Stacking II. HI content of the host galaxies of AGN: We use a stacking technique to measure the average HI content of a\nvolume-limited sample of 1871 AGN host galaxies from a parent sample of\ngalaxies selected from the SDSS and GALEX imaging surveys with stellar masses\ngreater than 10^10 M_sun and redshifts in the range 0.025~10^(43)erg/s) for the signatures of large-scale energetic outflows:\nextremely broad [O III] emission (FWHM ~ 700-1400km/s) across ~4-15kpc, with\nhigh velocity offsets from the systemic redshifts (up to ~850km/s). The four\nless luminous systems have lower quality data displaying weaker evidence for\nspatially extended outflows. We estimate that these outflows are potentially\ndepositing energy into their host galaxies at considerable rates\n(~10^(43)-10^(45)erg/s); however, due to the lack of constraints on the density\nof the outflowing material and the structure of the outflow, these estimates\nshould be taken as illustrative only. Based on the measured maximum velocities\n(v(max)~400-1400km/s) the outflows observed are likely to unbind some fraction\nof the gas from their host galaxies, but are unlikely to completely remove gas\nfrom the galaxy haloes. By using a combination of energetic arguments and a\ncomparison to ULIRGs without clear evidence for AGN activity, we show that the\nAGN activity could be the dominant power source for driving all of the observed\noutflows, although star formation may also play a significant role in some of\nthe sources.", "category": "astro-ph_CO" }, { "text": "Inferences of $H_0$ in presence of a non-standard recombination: Measurements of the Hubble parameter from the distance ladder are in tension\nwith indirect measurements based on the cosmic microwave background (CMB) data\nand the inverse distance ladder measurements at 3-4 $\\sigma$ level. We consider\nphenomenological modification to the timing and width of the recombination\nprocess and show that they can significantly affect this tension. This\npossibility is appealing, because such modification affects both the distance\nto the last scattering surface and the calibration of the baryon acoustic\noscillations (BAO) ruler. Moreover, because only a very small fraction of the\nmost energetic photons keep the early universe in the plasma state, it is\npossible that such modification could occur without affecting the energy\ndensity budget of the universe or being incompatible with the very tight limits\non the departure from the black-body spectrum of CMB. In particular, we find\nthat under this simplified model, with a conservative subset of Planck data\nalone, $H_0=73.44_{-6.77}^{+5.50}~{\\rm km\\ s}^{-1}\\ {\\rm Mpc}^{-1}$ and in\ncombination with BAO data $H_0=68.86_{-1.35}^{+1.31}~{\\rm km\\ s}^{-1}\\ {\\rm\nMpc}^{-1}$, decreasing the tension to $\\sim 2\\sigma$ level. However, when\ncombined with Planck lensing reconstruction and high-$\\ell$ polarization data,\nthe tension climbs back to $\\sim 2.7\\sigma$, despite the uncertainty on\nnon-ladder $H_0$ measurement more than doubling.", "category": "astro-ph_CO" }, { "text": "First Constraints on Small-Scale Non-Gaussianity from UV Galaxy\n Luminosity Functions: UV luminosity functions provide a wealth of information on the physics of\ngalaxy formation in the early Universe. Given that this probe indirectly tracks\nthe evolution of the mass function of dark matter halos, it has the potential\nto constrain alternative theories of structure formation. One of such scenarios\nis the existence of primordial non-Gaussianity at scales beyond those probed by\nobservations of the Cosmic Microwave Background. Through its impact on the halo\nmass function, such small-scale non-Gaussianity would alter the abundance of\ngalaxies at high redshifts. In this work we present an application of UV\nluminosity functions as measured by the Hubble Space Telescope to constrain the\nnon-Gaussianity parameter $f_\\mathrm{NL}$ for wavenumbers above a cut-off scale\n$k_{\\rm cut}$. After marginalizing over the unknown astrophysical parameters\nand accounting for potential systematic errors, we arrive at a $2\\sigma$ bound\nof $f_{\\rm NL}=71^{+426}_{-237}$ for a cut-off scale $k_{\\rm\ncut}=0.1\\,\\mathrm{Mpc}^{-1}$ in the bispectrum of the primordial gravitational\npotential. Moreover, we perform forecasts for the James Webb Space Telescope\nand the Nancy Grace Roman Space Telescope, finding an expected improvement of a\nfactor $3-4$ upon the current bound.", "category": "astro-ph_CO" }, { "text": "Redshift and distances in a \u039bCDM cosmology with non-linear\n inhomogeneities: Motivated by the dawn of precision cosmology and the wealth of forthcoming\nhigh precision and volume galaxy surveys, in this paper we study the effects of\ninhomogeneities on light propagation in a flat \\Lambda CDM background. To this\nend we use exact solutions of Einstein's equations (Meures & Bruni 2011) where,\nstarting from small fluctuations, inhomogeneities arise from a standard growing\nmode and become non-linear. While the matter distribution in these models is\nnecessarily idealised, there is still enough freedom to assume an arbitrary\ninitial density profile along the line of sight. We can therefore model\nover-densities and voids of various sizes and distributions, e.g. single\nharmonic sinusoidal modes, coupled modes, and more general distributions in a\n\\Lambda CDM background. Our models allow for an exact treatment of the light\npropagation problem, so that the results are unaffected by approximations and\nunambiguous. Along lines of sight with density inhomogeneities which average\nout on scales less than the Hubble radius, we find the distance redshift\nrelation to diverge negligibly from the Friedmann-Lemaitre-Robertson-Walker\n(FLRW) result. On the contrary, if we observe along lines of sight which do not\nhave the same average density as the background, we find large deviations from\nthe FLRW distance redshift relation. Hence, a possibly large systematic might\nbe introduced into the analysis of cosmological observations, e.g. supernovae,\nif we observe along lines of sight which are typically more or less dense than\nthe average density of the Universe. In turn, this could lead to wrong\nparameter estimation: even if the Cosmological Principle is valid, the\nidentification of the true FLRW background in an inhomogeneous universe maybe\nmore difficult than usually assumed.", "category": "astro-ph_CO" }, { "text": "The Stellar Halos of Massive Elliptical Galaxies II: Detailed Abundance\n Ratios at Large Radius: We study the radial dependence in stellar populations of 33 nearby early-type\ngalaxies with central stellar velocity dispersions sigma* > 150 km/s. We\nmeasure stellar population properties in composite spectra, and use ratios of\nthese composites to highlight the largest spectral changes as a function of\nradius. Based on stellar population modeling, the typical star at 2 R_e is old\n(~10 Gyr), relatively metal poor ([Fe/H] -0.5), and alpha-enhanced\n([Mg/Fe]~0.3). The stars were made rapidly at z~1.5-2 in shallow potential\nwells. Declining radial gradients in [C/Fe], which follow [Fe/H], also arise\nfrom rapid star formation timescales due to declining carbon yields from\nlow-metallicity massive stars. In contrast, [N/Fe] remains high at large\nradius. Stars at large radius have different abundance ratio patterns from\nstars in the center of any present-day galaxy, but are similar to Milky Way\nthick disk stars. Our observations are thus consistent with a picture in which\nthe stellar outskirts are built up through minor mergers with disky galaxies\nwhose star formation is truncated early (z~1.5-2).", "category": "astro-ph_CO" }, { "text": "The contribution of star-forming galaxies to fluctuations in the cosmic\n background light: Star-forming galaxies which are too faint to be detected individually produce\nintensity fluctuations in the cosmic background light. This contribution needs\nto be taken into account as a foreground when using the primordial signal to\nconstrain cosmological parameters. The extragalactic fluctuations are also\ninteresting in their own right as they depend on the star formation history of\nthe Universe and the way in which this connects with the formation of cosmic\nstructure. We present a new framework which allows us to predict the occupation\nof dark matter haloes by star-forming galaxies and uses this information, in\nconjunction with an N-body simulation of structure formation, to predict the\npower spectrum of intensity fluctuations in the infrared background. We compute\nthe emission from galaxies at far-infrared, millimetre and radio wavelengths.\nOur method gives accurate predictions for the clustering of galaxies both for\nthe one halo and two halo terms. We illustrate our new framework using a\npreviously published model which reproduces the number counts and redshift\ndistribution of galaxies selected by their emission at $850\\,\\mu$m. Without\nadjusting any of the model parameters, the predictions show encouraging\nagreement at high frequencies and on small angular scales with recent estimates\nof the extragalactic fluctuations in the background made from early data\nanalysed by the Planck Collaboration. There are, however, substantial\ndiscrepancies between the model predictions and observations on large angular\nscales and at low frequencies, which illustrates the usefulness of the\nintensity fluctuations as a constraint on galaxy formation models.", "category": "astro-ph_CO" }, { "text": "The VIMOS Public Extragalactic Redshift Survey (VIPERS): A quiescent\n formation of massive red-sequence galaxies over the past 9 Gyr: We explore the evolution of the Colour-Magnitude Relation (CMR) and\nLuminosity Function (LF) at 0.410^11 M_sun) and expeditious RS formation over a short\nperiod of ~1.5 Gyr starting before z=1. This is supported by the detection of\nongoing SF in ETGs at 0.9 = 2.7 \\pm 1.0 M\\odot yr-1, but do not show\nevidence of increasing star-formation rates toward the extreme 1.5 Mpc radius\nof the cluster. No individual cluster galaxy exceeds an SFR of 6 M\\odot yr-1 .\nMassive galaxies (log M\\ast /M\\odot > 10.75) all have low specific SFRs (SSFRs,\ni.e. SFR per unit stellar mass). At fixed stellar mass, galaxies in the cluster\ncentre have lower SSFRs than the rest of the cluster galaxies, which in turn\nhave lower SSFRs than field galaxies at the same redshift by a factor of a few\nto 10. For the first time we can demonstrate through measurements of individual\nSFRs that already at very early epochs (at an age of the Universe of \\sim4.5\nGyr) the suppression of star-formation is an effect of the cluster environment\nwhich persists at fixed galaxy stellar mass. [Erratum added after the original\npaper]", "category": "astro-ph_CO" }, { "text": "A common colour-magnitude relation from giant elliptical galaxies to\n globular clusters?: We discuss the existence of a common colour-magnitude relation (CMR) of\nmetal-poor globular clusters and early-type galaxies, i.e. giant ellipticals,\nnormal ellipticals and lenticulars, dwarf ellipticals and lenticulars, and\ndwarf spheroidals. Such CMR would cover a range of ~ 14 mag, extending from the\nbrightest galaxies, down to the globular clusters on the fainter side.", "category": "astro-ph_CO" }, { "text": "Application of the iterative reconstruction to simulated galaxy fields: We apply an iterative reconstruction method to galaxy mocks in redshift space\nobtained from $N$-body simulations. Comparing the two-point correlation\nfunctions for the reconstructed density field, we find that although the\nperformance is limited by shot noise and galaxy bias compared to the matter\nfield, the iterative method can still reconstruct the initial linear density\nfield from the galaxy field better than the standard method both in real and in\nredshift space. Furthermore, the iterative method is able to reconstruct both\nthe monopole and quadrupole more precisely, unlike the standard method. We see\nthat as the number density of galaxies gets smaller, the performance of\nreconstruction gets worse due to the sparseness. However, the precision in the\ndetermination of bias ($\\sim20\\%$) hardly impacts on the reconstruction\nprocesses.", "category": "astro-ph_CO" }, { "text": "Cosmic Dawn: Studies of the Earliest Galaxies and Their Role in Cosmic\n Reionization: I review recent progress and challenges in studies of the earliest galaxies,\nseen when the Universe was less than 1 billion years old. Can they be used as\nreliable tracers of the physics of cosmic reionization thereby complementing\nother, more direct, probes of the evolving neutrality of the intergalactic\nmedium? Were star-forming galaxies the primary agent in the reionization\nprocess and what are the future prospects for identifying the earliest systems\ndevoid of chemical enrichment? Ambitious future facilities are under\nconstruction for exploring galaxies and the intergalactic medium in the\nredshift range 6 to 20, corresponding to what we now consider the heart of the\nreionization era. I review what we can infer about this period from current\nobservations and in the near-future with existing facilities, and conclude with\na list of key issues where future work is required.", "category": "astro-ph_CO" }, { "text": "A candle in the wind: a radio filament in the core of the A3562 galaxy\n cluster: Using a MeerKAT observation of the galaxy cluster A3562 (a member of the\nShapley Supercluster), we have discovered a narrow, long and straight, very\nfaint radio filament, which branches out at a straight angle from the tail of a\nradio galaxy located in projection near the core of the cluster. The radio\nfilament spans 200 kpc and aligns with a sloshing cold front seen in the\nX-rays, staying inside the front in projection. The radio spectral index along\nthe filament appears uniform (within large uncertainties) at $\\alpha\\simeq\n-1.5$. We propose that the radio galaxy is located outside the cold front, but\ndips its tail under the front. The tangential wind that blows there may stretch\nthe radio plasma from the radio galaxy into a filamentary structure. Some\nreacceleration is needed in this scenario to maintain the radio spectrum\nuniform. Alternatively, the cosmic ray electrons from that spot in the tail can\nspread along the cluster magnetic field lines, straightened by that same\ntangential flow, via anomalously fast diffusion. Our radio filament can provide\nconstraints on this process. We also uncover a compact radio source at the\nBrightest Cluster Galaxy (BCG) that is 2--3 orders of magnitude less luminous\nthan those in typical cluster central galaxies -- probably an example of a BCG\nstarved of accretion fuel by gas sloshing.", "category": "astro-ph_CO" }, { "text": "Cosmological distances with general-relativistic ray tracing: framework\n and comparison to cosmographic predictions: In this work we present the first results from a new ray-tracing tool to\ncalculate cosmological distances in the context of fully nonlinear general\nrelativity. We use this tool to study the ability of the general cosmographic\nrepresentation of luminosity distance, as truncated at third order in redshift,\nto accurately capture anisotropies in the \"true\" luminosity distance. We use\nnumerical relativity simulations of cosmological large-scale structure\nformation which are free from common simplifying assumptions in cosmology. We\nfind the general, third-order cosmography is accurate to within 1% for\nredshifts to z\\approx 0.034 when sampling scales strictly above 100 Mpc/h,\nwhich is in agreement with an earlier prediction. We find the inclusion of\nsmall-scale structure generally spoils the ability of the third-order\ncosmography to accurately reproduce the full luminosity distance for wide\nredshift intervals, as might be expected. For a simulation sampling small-scale\nstructures, we find a +/- 5% variance in the monopole of the ray-traced\nluminosity distance at z \\approx 0.02. Further, all 25 observers we study here\nsee a 9--20% variance in the luminosity distance across their sky at z \\approx\n0.03, which reduces to 2--5% by z \\approx 0.1. These calculations are based on\nsimulations and ray tracing which adopt fully nonlinear general relativity, and\nhighlight the potential importance of fair sky-sampling in low-redshift\nisotropic cosmological analysis.", "category": "astro-ph_CO" }, { "text": "Proper Size of the Visible Universe in FRW Metrics with Constant\n Spacetime Curvature: In this paper, we continue to examine the fundamental basis for the\nFriedmann-Robertson-Walker (FRW) metric and its application to cosmology,\nspecifically addressing the question: What is the proper size of the visible\nuniverse? There are several ways of answering the question of size, though\noften with an incomplete understanding of how far light has actually traveled\nin reaching us today from the most remote sources. The difficulty usually\narises from an inconsistent use of the coordinates, or an over-interpretation\nof the physical meaning of quantities such as the so-called proper distance\nR(t)=a(t)r, written in terms of the (unchanging) co-moving radius r and the\nuniversal expansion factor a(t). In this paper, we use the five non-trivial FRW\nmetrics with constant spacetime curvature (i.e., the static FRW metrics, but\nexcluding Minkowski) to prove that in static FRW spacetimes in which expansion\nbegan from an initial signularity, the visible universe today has a proper size\nequal to R_h(t_0/2), i.e., the gravitational horizon at half its current age.\nThe exceptions are de Sitter and Lanczos, whose contents had pre-existing\npositions away from the origin. In so doing, we confirm earlier results showing\nthe same phenomenon in a broad range of cosmologies, including LCDM, based on\nthe numerical integration of null geodesic equations through an FRW metric.", "category": "astro-ph_CO" }, { "text": "A Search for Magnetized Quark Nuggets (MQNs), a Candidate for Dark\n Matter, Accumulating in Iron Ore: A search has been carried out for Magnetized Quark Nuggets (MQNs)\naccumulating in iron ore over geologic time. MQNs, which are theoretically\nconsistent with the Standard Models of Physics and of Cosmology, have been\nsuggested as dark-matter candidates. Indirect evidence of MQNs has been\npreviously inferred from observations of magnetars and of non-meteorite impact\ncraters. It is shown in this paper that MQNs can accumulate in taconite (iron\nore) and be transferred into ferromagnetic rod-mill liners during processing of\nthe ore. When the liners are recycled to make fresh steel, they are heated to\nhigher than the Curie temperature so that their ferromagnetic properties are\ndestroyed. The MQNs would then be released and fall into the ferromagnetic\nfurnace bottom where they would be trapped. Three such furnace bottoms have\nbeen magnetically scanned to search for the magnetic anomalies consistent with\ntrapped MQNs. The observed magnetic anomalies are equivalent to an accumulation\nrate of ~1 kg of MQNs per 1.2 x $10^8$ kg of taconite ore processed. The\nresults are consistent with MQNs but there could be other, unknown\nexplanations. We propose an experiment and calculations to definitively test\nthe MQN hypothesis for dark matter.", "category": "astro-ph_CO" }, { "text": "Neutrino masses from CMB B-mode polarization and cosmic growth rate: Constraints on neutrino masses are estimated based on future observations of\nthe cosmic microwave background (CMB), which includes the B-mode polarization\nproduced by CMB lensing from the Planck satellite, and the growth rate of\ncosmic structure from the Euclid redshift survey by using the Markov-Chain\nMonte-Carlo (MCMC) method. The error in the bound on the total neutrino mass is\nestimated to be $\\Delta\\sum m_{\\nu} = 0.075$ eV with a 68\\% confidence level.\nBy using the growth rate rather than the galaxy power spectrum, accurate\nconstraints are obtained, since the growth rate is less influenced by the\nuncertainty regarding galaxy bias than by the galaxy power spectrum.", "category": "astro-ph_CO" }, { "text": "Lensing convergence in galaxy clustering in LambdaCDM and beyond: We study the impact of neglecting lensing magnification in galaxy clustering\nanalyses for future galaxy surveys, considering the LambdaCDM model and two\nextensions: massive neutrinos and modifications of General Relativity. Our\nstudy focuses on the biases on the constraints and on the estimation of the\ncosmological parameters. We perform a comprehensive investigation of these two\neffects for the upcoming photometric and spectroscopic galaxy surveys Euclid\nand SKA for different redshift binning configurations. We also provide a\nfitting formula for the magnification bias of SKA. Our results show that the\ninformation present in the lensing contribution does improve the constraints on\nthe modified gravity parameters whereas the lensing constraining power is\nnegligible for the LambdaCDM parameters. For photometric surveys the estimation\nis biased for all the parameters if lensing is not taken into account. This\neffect is particularly significant for the modified gravity parameters.\nConversely for spectroscopic surveys the bias is below one sigma for all the\nparameters. Our findings show the importance of including lensing in galaxy\nclustering analyses for testing General Relativity and to constrain the\nparameters which describe its modifications.", "category": "astro-ph_CO" }, { "text": "Reconstructing the dark energy potential: Dark energy equation of state can be effectively described by that of a\nbarotropic fluid. The barotropic fluid model describes the background evolution\nand the functional form of the equation of state parameter is well constrained\nby the observations. Equally viable explanations of dark energy are via scalar\nfield models, both canonical and non-canonical; these scalar field models being\nlow energy descriptions of an underlying high energy theory. In this paper, we\nattempt to reconcile the two approaches to dark energy by way of reconstructing\nthe evolution of the scalar field potential. For this analysis, we consider\ncanonical quintessence scalar field and the phantom field for this\nreconstruction. We attempt to understand the analytical or semi-analytical\nforms of scalar field potentials corresponding to typical well behaved\nparameterisations of dark energy using the constraints from recent\nobservations.", "category": "astro-ph_CO" }, { "text": "Propagating Speed of Primordial Gravitational Waves: Primordial Gravitational Waves, i.e. a background of metric perturbations\nsourced by the quantum inflationary fluctuations, if measured, could both\nprovide a substantial evidence for primordial inflation and shed light on\nphysics at extremely high energy scales. In this work we focus on their\npropagating speed. Using an effective field theory approach we introduce a\ntime-dependent propagating speed $c_{\\rm T}(t)$ showing that also small\ndeviations from the General Relativity (GR) prediction $c_{\\rm T}(t) = c$ can\nlead to testable consequences. We derive a set of equations that relate the\npropagating speed and its time dependence to the inflationary parameters and\nthat generalize the usual slow roll consistency relations. Imposing the new\ngeneralized consistency relations and combining small and large scales data, we\nderive model independent constraints on inflation with non-trivial primordial\ntensor speed. In particular we constrain its scale dependence to be $d\\log\nc_{\\rm T} / d\\log k=0.082^{+0.047}_{-0.11}$ at 68% C.L. while we only derive\nthe lower bound $c_{\\rm T}>0.22\\,c$ at 95% C.L. . We also constrain the\ntensor-to-scalar ratio at the pivot scale $k_*=0.05\\rm{Mpc}^{-1}$ to be\n$r<0.0599$ at 95% C.L. in agreement with the result provided by the Planck\ncollaboration. Thanks to a proper small scale parameterization of the tensor\nspectrum we derive stringent constraints on the tensor tilt $n_{\\rm\nT}=-0.084^{+0.10}_{-0.047}$ at 68% C.L. and on its runnings $\\alpha_{\\rm\nT}=d\\,n_{\\rm T}/d\\log k=0.0141^{+0.0035}_{-0.021}$ and $\\beta_{\\rm\nT}=d\\,\\alpha_{\\rm T}/d\\log k= -0.0061^{+0.010}_{-0.0014}$ both at 68% C.L. Our\nresults show a remarkable agreement with the standard slow roll predictions and\nprove that current data can significantly constrain deviations from GR on the\ninflationary energy scales.", "category": "astro-ph_CO" }, { "text": "Cosmological constraints on the velocity-dependent baryon-dark matter\n coupling: We present the cosmological constraints on the cross section of baryon-dark\nmatter interactions for the dark matter mass below the MeV scale from the\nPlanck CMB (cosmic microwave background) and SDSS (Sloan Digital Sky Survey)\nLyman-$\\alpha$ forest data. To explore the dark matter mass $m_{\\chi}\\lesssim\n1$ MeV for which the dark matter's free-streaming effect can suppress the\nobservable small scale density fluctuations, in addition to the acoustic\noscillation damping in existence of the baryon-dark matter coupling, we apply\nthe approximated treatment of dark matter free-streaming analogous to that of\nthe conventional warm dark matter. We also demonstrate the mass dependence of\nthe baryon-dark matter cross section bounds (for the dark matter mass down to\n$m_{\\chi} \\sim 5~{\\rm keV}$), in contrast to the dark matter mass independence\nof the cross section constraints for the light dark matter below the MeV scale\nclaimed in the previous literature.", "category": "astro-ph_CO" }, { "text": "On the apparent absence of broad iron lines in Seyfert galaxies: We present an analysis of XMM-Newton observations of eleven Seyfert galaxies\nthat appear to be missing a broad iron K alpha line. These objects represent a\nchallenge to the established paradigm for active galactic nuclei, where a\nrelatively cold accretion disc feeds the central black hole. In that paradigm,\nX-ray illumination of the accretion disc should lead to continuum and\nfluorescence emission from iron which is broadened and shifted by relativistic\neffects close the hole. We extend the work of Nandra et al. (2007), who found\nno evidence for such a component in an earlier analysis of these objects, by\ntesting a variety of more complex relativistic reflection models. Specifically,\nwe consider the possibility that the disc is highly ionised, and/or that the\nthe reflection is heavily blurred by strong relativistic effects in a Kerr\ngeometry. We find that in 8/11 of the observations with no apparent broad iron\nline, the fit is significantly improved when an ionised or strongly blurred\nreflector is included, and that all 11 observations allow for such a component.\nThe disc inclinations are found generally to be around 60 degrees, which when\ncombined with a steep emissivity profile results in strong relativistic\nblurring of the reflection, rendering the K alpha line difficult to distinguish\nfrom the underlying continuum. Nevertheless, relativistic reflection does\nappear to be present, and the strength of the smeared reflection is similar to\nthat expected from a flat disc illuminated by a point source. Such blurred\nreflection and the associated steep radial emissivity profiles are consistent\nwith the gravitational light bending of the continuum photons close to the\nblack hole.", "category": "astro-ph_CO" }, { "text": "Gravitational lensing effects on sub-millimetre galaxy counts: We study the effects on the number counts of sub-millimetre galaxies due to\ngravitational lensing. We explore the effects on the magnification cross\nsection due to halo density profiles, ellipticity and cosmological parameter\n(the power-spectrum normalisation $\\sigma_8$). We show that the ellipticity\ndoes not strongly affect the magnification cross section in gravitational\nlensing while the halo radial profiles do. Since the baryonic cooling effect is\nstronger in galaxies than clusters, galactic haloes are more concentrated. In\nlight of this, a new scenario of two halo population model is explored where\ngalaxies are modeled as a singular isothermal sphere profile and clusters as a\nNavarro, Frenk and White (NFW) profile. We find the transition mass between the\ntwo has modest effects on the lensing probability. The cosmological parameter\n$\\sigma_8$ alters the abundance of haloes and therefore affects our results.\nCompared with other methods, our model is simpler and more realistic. The\nconclusions of previous works is confirm that gravitational lensing is a\nnatural explanation for the number count excess at the bright end.", "category": "astro-ph_CO" }, { "text": "A fast and accurate method to compute the mass return from multiple\n stellar populations: The mass returned to the ambient medium by aging stellar populations over\ncosmological times sums up to a significant fraction (20% - 30% or more) of\ntheir initial mass. This continuous mass injection plays a fundamental role in\nphenomena such as galaxy formation and evolution, fueling of supermassive black\nholes in galaxies and the consequent (negative and positive) feedback\nphenomena, and the origin of multiple stellar populations in globular clusters.\nIn numerical simulations the calculation of the mass return can be time\nconsuming, since it requires at each time step the evaluation of a convolution\nintegral over the whole star formation history, so the computational time\nincreases quadratically with the number of time-steps. The situation can be\nespecially critical in hydrodynamical simulations, where different grid points\nare characterized by different star formation histories, and the gas cooling\nand heating times are shorter by orders of magnitude than the characteristic\nstellar lifetimes. In this paper we present a fast and accurate method to\ncompute the mass return from stellar populations undergoing arbitrarily\ncomplicated star formation histories. At each time-step the mass return is\ncalculated from its value at the previous time, and the star formation rate\nover the last time-step only. Therefore in the new scheme there is no need to\nstore the whole star formation history, and the computational time increases\nlinearly with the number of time-steps.", "category": "astro-ph_CO" }, { "text": "The origin of dispersion in DLA metallicities: Recent chemical abundance measurements of damped Ly-alpha absorbers (DLAs)\nrevealed an intrinsic scatter in their metallicity of ~0.5 dex out to z~5. In\norder to explore the origin of this scatter, we build a semi-analytic model\nwhich traces the chemical evolution of the interstellar matter in small regions\nof the Universe with different mean density, from over- to underdense regions.\nWe show that the different histories of structure formation in these regions,\nnamely halo abundance, mass and stellar content, is reflected in the chemical\nproperties of the protogalaxies, and in particular of DLAs. We calculate mean\nmetallicity-redshift relations and show that the metallicity dispersion arising\nfrom this environmental effect amounts to ~0.25 dex and is an important\ncontributor to the observed overall intrinsic scatter.", "category": "astro-ph_CO" }, { "text": "Isotropy of low redshift type Ia Supernovae: A Bayesian analysis: The standard cosmology strongly relies upon the Cosmological Principle, which\nconsists on the hypotheses of large scale isotropy and homogeneity of the\nUniverse. Testing these assumptions is, therefore, crucial to determining if\nthere are deviations from the standard cosmological paradigm. In this paper, we\nuse the latest type Ia supernova compilations, namely JLA and Union2.1 to test\nthe cosmological isotropy at low redshift ranges ($z<0.1$). This is performed\nthrough a Bayesian selection analysis, in which we compare the standard,\nisotropic model, with another one including a dipole correction due to peculiar\nvelocities. We find that the Union2.1 sample favors the dipole-corrected model,\nbut the opposite happens for the JLA. Nonetheless, the velocity dipole results\nare in good agreement with previous analyses carried out with both datasets. We\nconclude that there are no significant indications for large anisotropic\nsignals from nearby supernova compilations, albeit this test should be greatly\nimproved with the upcoming cosmological surveys.", "category": "astro-ph_CO" }, { "text": "Optimal filtering of optical and weak lensing data to search for galaxy\n clusters: application to the COSMOS field: Galaxy clusters are usually detected in blind optical surveys via suitable\nfiltering methods. We present an optimal matched filter which maximizes their\nsignal-to-noise ratio by taking advantage of the knowledge we have of their\nintrinsic physical properties and of the data noise properties. In this paper\nwe restrict our application to galaxy magnitudes, positions and photometric\nredshifts if available, and we also apply the filter separately to weak lensing\ndata. The method is suitable to be naturally extended to a multi-band approach\nwhich could include not only additional optical bands but also observables with\ndifferent nature such as X-rays. For each detection, the filter provides its\nsignificance, an estimate for the richness and for the redshift even if photo-z\nare not given. The provided analytical error estimate is tested against\nnumerical simulations. We finally apply our method to the COSMOS field and\ncompare the results with previous cluster detections obtained with different\nmethods. Our catalogue contains 27 galaxy clusters with minimal threshold at\n3-sigma level including both optical and weak-lensing information.", "category": "astro-ph_CO" }, { "text": "Clusters in the Disperse cosmic web: Galaxy cluster mass halos (\"clusters\") in a dark matter simulation are\nmatched to nodes in several different cosmic webs found using the Disperse\ncosmic web finder. The webs have different simulation smoothings and Disperse\nparameter choices; for each, 4 methods are considered for matching Disperse\nnodes to clusters. For most of the webs, Disperse nodes outnumber clusters, but\nnot every cluster has a Disperse node match (and sometimes $>1$ cluster matches\nto the same Disperse node). The clusters frequently lacking a matching Disperse\nnode have a different distribution of local shear trends and perhaps merger\nhistories. It might be interesting to see in what other ways, e.g.,\nobservational properties, these clusters differ. For the webs with smoothing\n$\\leq$ 2.5 $Mpc/h$, and all but the most restrictive matching criterion,\n$\\sim$3/4 of the clusters always have a Disperse node counterpart. The nearest\ncluster to a given Disperse node and vice versa, within twice the smoothing\nlength, obey a cluster mass-Disperse node density relation. Cluster pairs where\nboth clusters match Disperse nodes can also be assigned the filaments between\nthose nodes, but as the web and matching methods are varied, most such\nfilaments do not remain. There is an enhancement of subhalo counts and halo\nmass between cluster pairs, averaging over cluster pairs assigned Disperse\nfilaments increases the enhancement. The approach here also lends itself to\ncomparing nodes across many cosmic web constructions, using the fixed\nunderlying cluster distribution to make a correspondence.", "category": "astro-ph_CO" }, { "text": "Extraterrestrial Axion Search with the Breakthrough Listen Galactic\n Center Survey: Axion dark matter (DM) may efficiently convert to photons in the\nmagnetospheres of neutron stars (NSs), producing nearly monochromatic radio\nemission. This process is resonantly triggered when the plasma frequency\ninduced by the underlying charge distribution approximately matches the axion\nmass. We search for evidence of this process using archival Green Bank\nTelescope data collected in a survey of the Galactic Center in the C-Band by\nthe Breakthrough Listen project. While Breakthrough Listen aims to find\nsignatures of extraterrestrial life in the radio band, we show that their\nhigh-frequency resolution spectral data of the Galactic Center region is ideal\nfor searching for axion-photon transitions generated by the population of NSs\nin the inner pc of the Galaxy. We use data-driven models to capture the\ndistributions and properties of NSs in the inner Galaxy and compute the\nexpected radio flux from each NS using state-of-the-art ray tracing\nsimulations. We find no evidence for axion DM and set leading constraints on\nthe axion-photon coupling, excluding values down to the level $g_{a \\gamma\n\\gamma} \\sim 10^{-11}$ GeV$^{-1}$ for DM axions for masses between 15 and 35\n$\\mu$eV.", "category": "astro-ph_CO" }, { "text": "Is $w \\neq -1$ evidence for a dynamical dark energy equation of state ?: Current constraints on the dark energy equation of state parameter, $w$, are\nexpected to be improved by more than one order of magnitude in the next decade.\nIf $|w-1| \\gsim 0.01$ around the present time, but the dark energy dynamics is\nsufficiently slow, it is possible that future constraints will rule out a\ncosmological constant while being consistent with a time-independent equation\nof state parameter. In this paper, we show that although models with such\nbehavior can be constructed, they do require significant fine-tuning.\nTherefore, if the observed acceleration of the Universe is induced by a dark\nenergy component, then finding $w \\neq -1$ would, on its own, constitute very\nstrong evidence for a dynamical dark energy equation of state.", "category": "astro-ph_CO" }, { "text": "Does a 'stochastic' background of gravitational waves exist in the\n pulsar timing band?: We investigate the effects of gravitational waves (GWs) from a simulated\npopulation of binary super-massive black holes (SMBHs) on pulsar timing array\ndatasets. We construct a distribution describing the binary SMBH population\nfrom an existing semi-analytic galaxy formation model. Using realizations of\nthe binary SMBH population generated from this distribution, we simulate pulsar\ntiming datasets with GW-induced variations. We find that the statistics of\nthese variations do not correspond to an isotropic, stochastic GW background.\nThe \"Hellings & Downs\" correlations between simulated datasets for different\npulsars are recovered on average, though the scatter of the correlation\nestimates is greater than expected for an isotropic, stochastic GW background.\nThese results are attributable to the fact that just a few GW sources dominate\nthe GW-induced variations in every Fourier frequency bin of a 5-year dataset.\nCurrent constraints on the amplitude of the GW signal from binary SMBHs will be\nbiased. Individual binary systems are likely to be detectable in 5-year pulsar\ntiming array datasets where the noise is dominated by GW-induced variations.\nSearches for GWs in pulsar timing array data therefore need to account for the\neffects of individual sources of GWs.", "category": "astro-ph_CO" }, { "text": "Scale-invariant enhancement of gravitational waves during inflation: The inflationary 1-loop tensor power spectrum from an excited spectator\nscalar field is calculated. Recent studies on primordial black holes suggest\nthat the inflationary curvature perturbation may be huge on small scales. An\nenhanced curvature perturbation may arise from a drastic enhancement of\nspectator scalar field fluctuations. In this letter, using the in-in formalism,\nwe calculate 1-loop quantum corrections to primordial gravitational waves by\nsuch an excited spectator field with a sharp peak in momentum space. We find\nscale-invariant loop corrections in this full quantum setup, in contrast to the\nsharply peaked corrections in the previously calculated scalar-induced tensor\nmodes. Especially, on super Hubble scales, the primordial gravitational waves\nare also amplified, which can be understood as a Bogolyubov transformation of\nthe vacuum due to the excited scalar field. This mechanism allows us to probe\nthe scalar field properties on extremely short-distance scales with the current\nand future cosmic microwave background and gravitational wave experiments,\nopening a novel window for inflationary cosmology.", "category": "astro-ph_CO" }, { "text": "Witnessing the Formation of a Brightest Cluster Galaxy in a Nearby X-ray\n Cluster: The central dominant galaxies in galaxy clusters constitute the most massive\nand luminous galaxies in the Universe. Despite this, the formation of these\nbrightest cluster galaxies (BCGs) and the impact of this on the surrounding\ncluster environment remain poorly understood. Here we present multi-wavelength\nobservations of the nearby poor X-ray cluster MZ 10451, in which both processes\ncan be studied in unprecedented detail. Chandra observations of the\nintracluster medium (ICM) in the cluster core, which harbors two optically\nbright early-type galaxies in the process of merging, show that the system has\nretained a cool core and a central metal excess. This suggests that any\nmerger-induced ICM heating and mixing remain modest at this stage. Tidally\nstripped stars seen around either galaxy likely represent an emerging\nintracluster light component, and the central ICM abundance enhancement may\nhave a prominent contribution from in situ enrichment provided by these stars.\nThe smaller of the merging galaxies shows evidence for having retained a hot\ngas halo, along with tentative evidence for some obscured star formation,\nsuggesting that not all BCG major mergers at low redshift are completely\ndissipationless. Both galaxies are slightly offset from the peak of the ICM\nemission, with all three lying on an axis that roughly coincides with the\nlarge-scale elongation of the ICM. Our data are consistent with a picture in\nwhich central BCGs are built up by mergers close to the cluster core, by\ngalaxies infalling on radial orbits aligned with the cosmological filaments\nfeeding the cluster.", "category": "astro-ph_CO" }, { "text": "The Cosmic Web of Baryons: Only about 10% of the baryons in the universe lie in galaxies as stars or\ncold gas, with the remainder predicted to exist as a dilute gaseous filamentary\nnetwork known as the Cosmic Web. Some of this gas is detected through UV\nabsorption line studies, but half of the gas remains undetected. Growth of\nstructure simulations suggest that these \"missing\" baryons were shock heated in\nunvirialized cosmic filaments to temperatures of 10^5.5-10^7 K, and that the\ngas is chemically enriched by galactic superwinds. Most of the gas in this\ntemperature regime can be detected only by X-ray observations through\nabsorption and emission from the He-like and H-line ions of C, N, and O. This\nwhite paper shows that an X-ray telescope such as IXO can test the most central\npredictions of the Cosmic Web: the distribution of gas mass with temperature;\nthe dynamics of the gas and its relationship to nearby galaxies; and the\ntopology of the Cosmic Web material.", "category": "astro-ph_CO" }, { "text": "Mass-radius relation of Newtonian self-gravitating Bose-Einstein\n condensates with short-range interactions: II. Numerical results: We develop the suggestion that dark matter could be a Bose-Einstein\ncondensate. We determine the mass-radius relation of a Newtonian\nself-gravitating Bose-Einstein condensate with short-range interactions\ndescribed by the Gross-Pitaevskii-Poisson system. We numerically solve the\nequation of hydrostatic equilibrium describing the balance between the\ngravitational attraction and the pressure due to quantum effects (Heisenberg's\nuncertainty principle) and short-range interactions (scattering). We connect\nthe non-interacting limit to the Thomas-Fermi limit. We also consider the case\nof attractive self-interaction. We compare the exact mass-radius relation\nobtained numerically with the approximate analytical relation obtained with a\nGaussian ansatz. An overall good agreement is found.", "category": "astro-ph_CO" }, { "text": "Primordial non-gaussianity from the bispectrum of 21-cm fluctuations in\n the dark ages: A measurement of primordial non-gaussianity will be of paramount importance\nto distinguish between different models of inflation. Cosmic microwave\nbackground (CMB) anisotropy observations have set unprecedented bounds on the\nnon-gaussianity parameter f_NL but the interesting regime f_NL <~ 1 is beyond\ntheir reach. Brightness-temperature fluctuations in the 21-cm line during the\ndark ages (z ~ 30-100) are a promising successor to CMB studies, giving access\nto a much larger number of modes. They are, however, intrinsically non-linear,\nwhich results in secondary non-gaussianities orders of magnitude larger than\nthe sought-after primordial signal. In this paper we carefully compute the\nprimary and secondary bispectra of 21-cm fluctuations on small scales. We use\nthe flat-sky formalism, which greatly simplifies the analysis, while still\nbeing very accurate on small angular scales. We show that the secondary\nbispectrum is highly degenerate with the primordial one, and argue that even\npercent-level uncertainties in the amplitude of the former lead to a bias of\norder Delta f_NL ~ 10. To tackle this problem we carry out a detailed Fisher\nanalysis, marginalizing over the amplitudes of a few smooth redshift-dependent\ncoefficients characterizing the secondary bispectrum. We find that the\nsignal-to-noise ratio for a single redshift slice is reduced by a factor of ~5\nin comparison to a case without secondary non-gaussianities. Setting aside\nforeground contamination, we forecast that a cosmic-variance-limited experiment\nobserving 21-cm fluctuations over 30 < z < 100 with a 0.1-MHz bandwidth and\n0.1-arcminute angular resolution could achieve a sensitivity of order\nf_NL[local] ~ 0.03, f_NL[equilateral] ~ 0.04, and f_NL[orthogonal] ~ 0.03.", "category": "astro-ph_CO" }, { "text": "Is the expansion of the universe accelerating? All signs still point to\n yes a local dipole anisotropy cannot explain dark energy: Type Ia supernovae (SNe Ia) provided the first strong evidence that the\nexpansion of the universe is accelerating. With SN samples now more than ten\ntimes larger than those used for the original discovery and joined by other\ncosmological probes, this discovery is on even firmer ground. Two recent,\nrelated studies (Nielsen et al. 2016 and Colin et al. 2019, hereafter N16 and\nC19, respectively) have claimed to undermine the statistical significance of\nthe SN Ia constraints. Rubin & Hayden (2016) (hereafter RH16) showed N16 made\nan incorrect assumption about the distributions of SN Ia light-curve\nparameters, while C19 also fails to remove the impact of the motion of the\nsolar system from the SN redshifts, interpreting the resulting errors as\nevidence of a dipole in the deceleration parameter. Building on RH16, we\noutline the errors C19 makes in their treatment of the data and inference on\ncosmological parameters. Reproducing the C19 analysis with our proposed fixes,\nwe find that the dipole parameters have little effect on the inferred\ncosmological parameters. We thus affirm the conclusion of RH16: the evidence\nfor acceleration is secure.", "category": "astro-ph_CO" }, { "text": "Bayesian evidence of the post-Planck curvaton: We perform a Bayesian model comparison for scenarios within the quadratic\ncurvaton model, determining the degree to which both are disfavoured with\nrespect to the $\\Lambda$CDM concordance model and single-field quadratic\ninflation, using the recent \\emph{Planck} data release. Despite having three\nadditional model parameters, the simplest curvaton scenario is not disfavoured\nrelative to single-field quadratic inflation, and it becomes favoured against\nthis single-field model when we include the joint BICEP/Keck/\\emph{Planck}\nanalysis. In all cases we assume an instantaneous inflaton decay and no\nsurviving isocurvature perturbations. Despite the success of \\emph{Planck}\nreaching its forecast measurement accuracy, we show that the current\nconstraints on local non-Gaussianity are insufficiently precise to have any\nsignificant impact on the evidence ratios so far. We also determine the\nprecision $\\sigma(f_{\\mathrm{NL}})$ required by future measurements assuming a\nfiducial value of $f_{\\mathrm{NL}}=-5/4$ or $10.8$ to no longer disfavour the\ncurvaton against the $\\Lambda$CDM parametrisation, and we discuss the effect\nthat the predicted increase in precision from future measurements on\n$f_{\\mathrm{NL}}$ may have. We show that our results are not very sensitive to\nour choice of priors.", "category": "astro-ph_CO" }, { "text": "Introduction to Early Universe Cosmology: Observational cosmology is in its \"golden age\" with a vast amount of recent\ndata on the distribution of matter and light in the universe. This data can be\nused to probe theories of the very early universe. It is small amplitude\ncosmological fluctuations which encode the information about the very early\nuniverse and relate it to current data. Hence, a central topic in these\nlectures is the \"theory of cosmological perturbations\", the theory which\ndescribes the generation of inhomogeneities in the very early universe and\ntheir evolution until the current time. I will apply this theory to three\nclasses of models of the very early universe. The first is \"Inflationary\nCosmology\", the current paradigm for understanding the early evolution of the\nuniverse. I will review the successes of inflationary cosmology, but will also\nfocus on some conceptual challenges which inflationary cosmology is facing,\nchallenges which motivate the search for possible alternatives. I will\nintroduce two alternative scenarios, the \"Matter Bounce\" model and \"String Gas\nCosmology\", and I will discuss how cosmological fluctuations which can explain\nthe current data are generated in those models.", "category": "astro-ph_CO" }, { "text": "A New Constraint on the Simulation of the Intergalactic Medium through\n the Evolution of the Neutral Hydrogen Fraction in the Epoch of Reionization: The thermal history of the intergalactic medium is full of extremely useful\ndata in the field of astrophysics and cosmology. In other words, by examining\nthis environment in different redshifts, the effects of cosmology and\nastrophysics can be observed side by side. Therefore, simulation is our very\npowerful tool to reach a suitable model for the intergalactic medium, both in\nterms of cosmology and astrophysics. In this work, we have simulated the\nintergalactic medium with the help of the 21cmFAST code and compared the\nevolution of the neutral hydrogen fraction in different initial conditions.\nConsiderable works arbitrarily determine many important effective parameters in\nthe thermal history of the intergalactic medium without any constraints, and\nusually, there is a lot of flexibility for modeling. Nonetheless, in this work,\nby focusing on the evolution of the neutral hydrogen fraction in different\nmodels and comparing it with observational data, we have eliminated many models\nand introduced only limited simulation models that could confirm the\nobservations with sufficient accuracy. This issue becomes thoroughly vital from\nthe point that, in addition to restricting the models through the neutral\nhydrogen fraction, it can also impose restrictions on the parameters affecting\nits changes. However, we hope that in future works, by enhancing the\nobservational data and increasing their accuracy, more compatible models with\nthe history of the intergalactic medium can be achieved.", "category": "astro-ph_CO" }, { "text": "Measuring Microlensing using Spectra of Multiply Lensed Quasars: We report on a program of spectroscopic observations of\ngravitationally-lensed QSOs with multiple images. We seek to establish whether\nmicrolensing is occurring in each QSO image using only single-epoch\nobservations. We calculate flux ratios for the cores of emission lines in image\npairs to set a baseline for no microlensing. The offset of the continuum flux\nratios relative to this baseline yields the microlensing magnification free\nfrom extinction, as extinction affects the continuum and the lines equally.\nWhen we find chromatic microlensing, we attempt to constrain the size of the\nQSO accretion disk. SDSSJ1004+4112 and HE1104-1805 show chromatic microlensing\nwith amplitudes $0.2< |\\Delta m| < 0.6$ and $0.2< |\\Delta m| < 0.4$ mag,\nrespectively. Modeling the accretion disk with a Gaussian source ($I\\propto\n\\exp(-R^2/2r_s^2)$) of size $r_s\\propto \\lambda^p$ and using magnification maps\nto simulate microlensing we find $r_s(\\lambda 3363)=7\\pm3 light-days\n(18.1\\pm7.8 \\times 10^{15} cm$) and $p=1.1\\pm 0.4$ for SDSS1004+4112, and\n$r_s(\\lambda 3363)=6\\pm2 light-days (15.5\\pm5.2 \\times 10^{15} cm$) and\n$p=0.7\\pm0.1$ for HE1104-1805. For SDSSJ1029+2623 we find strong chromaticity\nof $\\sim 0.4$ mag in the continuum flux ratio, which probably arises from\nmicrolensing although not all the available data fit within this explanation.\nFor Q0957+561 we measure B-A magnitude differences of 0.4 mag, much greater\nthan the $\\sim$0.05 mag amplitude usually inferred from lightcurve variability.\nIt may substantially modify the current interpretations of microlensing in this\nsystem, likely favoring the hypothesis of smaller sources and/or larger\nmicrodeflectors. For HS0818+1227, our data yield posible evidence of\nmicrolensing.", "category": "astro-ph_CO" }, { "text": "Vector field instability and the primordial tensor spectrum: It has recently been shown that the presence of a spectator pseudoscalar\nfield, coupled to photons through a Chern-Simons term, can amplify the\nprimordial tensor spectrum without observationally disrupting the primordial\nscalar spectrum. The amplification occurs due to an instability that develops\nfor the vector fields. We consider the extension of previous studies to account\nfor the contribution arising from an inhomogeneous vector background which is\ngenerated prior to the onset of inflation. We find that there may be\ncontributions in which net momentum is transferred between the inhomogeneous\nvector background and the gravitons, which would give rise to a signature\ndifferent than in the absence of the semiclassical corrections. We discuss the\nproperties the classical vector field form must have in order for these\nsignatures to leave observable imprints, though we were unable to construct a\nmodel for generating such a vector field.", "category": "astro-ph_CO" }, { "text": "The Epoch of Reionization in the R_h=ct Universe: The measured properties of the epoch of reionization (EoR) show that\nreionization probably began around z ~ 12-15 and ended by z=6. In addition, a\ncareful analysis of the fluctuations in the cosmic microwave background\nindicate a scattering optical depth tau ~ 0.066+/-0.012 through the EoR. In the\ncontext of LCDM, galaxies at intermediate redshifts and dwarf galaxies at\nhigher redshifts now appear to be the principal sources of UV ionizing\nradiation, but only for an inferred (ionizing) escape fraction f_ion ~ 0.2,\nwhich is in tension with other observations that suggest a value as small as ~\n0.05. In this paper, we examine how reionization might have progressed in the\nalternative Friedmann-Robertson Walker cosmology known as the R_h=ct Universe,\nand determine the value of f_ion required with this different rate of\nexpansion. We find that R_h=ct accounts quite well for the currently known\nproperties of the EoR, as long as its fractional baryon density falls within\nthe reasonable range 0.026 < Omega_b < 0.037. This model can also fit the EoR\ndata with f_ion ~ 0.05, but only if the Lyman continuum photon production is\nhighly efficient and Omega_b ~ 0.037. These results are still preliminary,\nhowever, given their reliance on a particular form of the star-formation rate\ndensity, which is still uncertain at very high redshifts. It will also be\nhelpful to reconsider the EoR in R_h=ct when complete structure formation\nmodels become available.", "category": "astro-ph_CO" }, { "text": "The Spitzer Extragalactic Representative Volume Survey (SERVS): The\n Environments of High-z SDSS Quasi-Stellar-Objects: This paper presents a study of the environments of SDSS Quasi-Stellar-Objects\n(QSOs) in the Spitzer Extragalactic Representative Volume Survey (SERVS). We\nconcentrate on the high-redshift QSOs as these have not been studied in large\nnumbers with data of this depth before. We use the IRAC 3.6-4.5{\\mu}m colour of\nobjects and ancillary r-band data to filter out as much foreground\ncontamination as possible. This technique allows us to find a significant (>\n4-{\\sigma}) over-density of galaxies around QSOs in a redshift bin centred on z\n~ 2.0 and a (> 2-{\\sigma}) over-density of galaxies around QSOs in a redshift\nbin centred on z ~ 3.3. We compare our findings to the predictions of a\nsemi-analytic galaxy formation model, based on the {\\Lambda}CDM millennium\nsimulation, and find for both redshift bins that the model predictions match\nwell the source-density we have measured from the SERVS data.", "category": "astro-ph_CO" }, { "text": "(Mis-)Interpreting supernovae observations in a lumpy universe: Light from `point sources' such as supernovae is observed with a beam width\nof order of the sources' size - typically less than 1 AU. Such a beam probes\nmatter and curvature distributions that are very different from coarse-grained\nrepresentations in N-body simulations or perturbation theory, which are\nsmoothed on scales much larger than 1 AU. The beam typically travels through\nunclustered dark matter and hydrogen with a mean density much less than the\ncosmic mean, and through dark matter halos and hydrogen clouds. Using N-body\nsimulations, as well as a Press-Schechter approach, we quantify the density\nprobability distribution as a function of beam width and show that, even for\nGpc-length beams of 500 kpc diameter, most lines of sight are significantly\nunder-dense. From this we argue that modelling the probability distribution for\nAU-diameter beams is absolutely critical. Standard analyses predict a huge\nvariance for such tiny beam sizes, and nonlinear corrections appear to be\nnon-trivial. It is not even clear whether under-dense regions lead to dimming\nor brightening of sources, owing to the uncertainty in modelling the expansion\nrate which we show is the dominant contribution. By considering different\nreasonable approximations which yield very different cosmologies we argue that\nmodelling ultra-narrow beams accurately remains a critical problem for\nprecision cosmology. This could appear as a discordance between angular\ndiameter and luminosity distances when comparing SN observations to BAO or CMB\ndistances.", "category": "astro-ph_CO" }, { "text": "The Abundance Scatter in M33 from HII Regions: Is There Any Evidence for\n Azimuthal Metallicity Variations?: Optical spectra of 25 H II regions in the inner two kpc of the M33 disk have\nbeen obtained with the GMOS spectrograph at the Gemini North telescope. The\noxygen abundance gradient measured from the detection of the [O III]4363\nauroral line displays a scatter of approximately 0.06 dex, a much smaller value\nthan recently reported by Rosolowsky & Simon in this galaxy. The analysis of\nthe abundances for a large sample of H II regions derived from the R23\nstrong-line indicator confirms that the scatter is small over the full disk of\nM33, consistent with the measuring uncertainties, and comparable to what is\nobserved in other spiral galaxies. No evidence is therefore found for\nsignificant azimuthal variations in the present-day metallicity of the\ninterstellar medium in this galaxy on spatial scales from ~100 pc to a few kpc.\nA considerable fraction of M33 H II regions with auroral line detections show\nspectral features revealing sources of hard ionizing radiation (such as He II\nemission and large [Ne III], [O III] line fluxes). Since R23 is shown to\nseverely underestimate the oxygen abundances in such cases, care must be taken\nin chemical abundance studies of extragalactic H II regions based on this\nstrong-line indicator.", "category": "astro-ph_CO" }, { "text": "Reconstruction of Power Spectrum of Primordial Curvature Perturbations\n on small scales from Primordial Black Hole Binaries scenario of LIGO/VIRGO\n detection: As a candidate bound for the Binary Black Hole (BBH) merger events detected\nby LIGO/Virgo, Primordial Black Holes (PBHs) provide a useful tool to\ninvestigate the primordial curvature perturbations on small scales. Using the\nGWTC-1 to GWTC-3 catalogs, under the scenario that PBHs originate from large\nprimordial curvature perturbations on small scales during inflationary epoch,\nwe for the first time reconstruct the power spectrum of primordial curvature\nperturbations on small scales. It is found that the value of the amplitude of\nthe primordial power spectrum is enhanced to $\\mathcal{O}(10^{-2})$ on scales\n$\\mathcal{O}(1)$ pc. This may imply the validity of PBH as a possible BBH\nmerger candidate.", "category": "astro-ph_CO" }, { "text": "Blue Fermi Flat Spectrum Radio Quasars: Many blazars detected by the Fermi satellite, observed spectroscopically in\nthe optical, are line-less, and have been classified as BL Lac objects.\nOptical-UV photometry of nearly one hundred of them allowed to determine the\nredshift for a handful of objects and redshift upper limits for the great\nmajority. A few of these are candidates to be \"blue quasars\", namely flat\nspectrum radio quasars whose broad emission lines are hidden by an overwhelming\nsynchrotron emission peaking in the UV. This implies that the emitting\nelectrons have high energies. In turn, this requires relatively weak radiative\ncooling, a condition that can be met if the main radiative dissipation of the\njet power occurs outside the broad line region. We confirm this hypothesis by\nstudying and modelling the spectral energy distributions of the 4 \"blue\nquasars\" recently discovered. Furthermore, we discuss the distribution of Fermi\nblazars in the gamma-ray spectral index -- gamma-ray luminosity plane, and\nargue that \"blue quasars\" objects are a minority within the blazar populations.", "category": "astro-ph_CO" }, { "text": "Internal dynamics of Abell 1240: a galaxy cluster with symmetric double\n radio relics: We aim to obtain new insights into the internal dynamics of the cluster Abell\n1240, showing the presence of two roughly symmetric radio relics, separated by\n~2 h_70^-1 Mpc. Our analysis is mainly based on redshift data for 145 galaxies\nand on new photometric data. We also use X-ray data from the Chandra archive\nand photometric data from the SDSS (DR7). We combine galaxy velocities and\npositions to select 89 cluster galaxies and analyze the internal dynamics of\nthe Abell 1237 + Abell 1240 cluster complex. We estimate similar redshifts for\nAbell 1237 and Abell 1240, =0.1935 and =0.1948, respectively. For Abell\n1237 we estimate velocity dispersion sigma_v~740 km/s and a mass M~6 10^14\nh_70^-1 M_sun. For Abell 1240 we estimate a LOS sigma_v~870 km/s and a mass\nrange M~0.9-1.9 10^15 h_70^-1 M_sun, which takes into account its complex\ndynamics. Abell 1240 is shown to have a bimodal structure with two galaxy\nclumps roughly defining the N-S direction, the same one defined by the\nelongation of its X-ray surface brightness and by the axis of symmetry of the\nrelics. The two--body model agrees with the hypothesis that we are looking at a\ncluster merger occurred largely in the plane of the sky, with the two galaxy\nclumps separated by a rest-frame velocity difference V_rf~2000 km/s at a time\nof 0.3 Gyrs after the crossing core, while Abell 1237 is still infalling onto\nAbell 1240. Chandra archive data confirm the complex structure of Abell 1240\nand allow us to estimate a global X-ray temperature T_X=6.0+-0.5 keV. In\nagreement with the findings from radio data, our results for Abell 1240\nstrongly support the \"outgoing merger shocks\" model to explain the presence of\nthe relics.", "category": "astro-ph_CO" }, { "text": "Broadband Imaging Segregation of z ~ 3 Ly-alpha Emitting and Ly-alpha\n Absorbing Galaxies: The spectral properties of Lyman break galaxies (LBGs) offer a means to\nisolate pure samples displaying either dominant Ly-alpha in absorption or\nLy-alpha in emission using broadband information alone. We present criteria\ndeveloped using a large z ~ 3 LBG spectroscopic sample from the literature that\nenables large numbers of each spectral type to be gathered in photometric data,\nproviding good statistics for multiple applications. In addition, we find that\nthe truncated faint, blue-end tail of z ~ 3 LBG population overlaps and leads\ndirectly into an expected Ly-alpha emitter (LAE) population. As a result, we\npresent simple criteria to cleanly select large numbers of z ~ 3 LAEs in deep\nbroadband surveys. We present the spectroscopic results of 32 r' <~ 25.5 LBGs\nand r' <~ 27.0 LAEs at z ~ 3 pre-selected in the Canada-France-Hawaii Telescope\nLegacy Survey that confirm these criteria.", "category": "astro-ph_CO" }, { "text": "All-Sky Analysis of the General Relativistic Galaxy Power Spectrum: We perform an all-sky analysis of the general relativistic galaxy power\nspectrum using the well-developed spherical Fourier decomposition. Spherical\nFourier analysis expresses the observed galaxy fluctuation in terms of the\nspherical harmonics and spherical Bessel functions that are angular and radial\neigenfunctions of the Helmholtz equation, providing a natural orthogonal basis\nfor all-sky analysis of the large-scale mode measurements. Accounting for all\nthe relativistic effects in galaxy clustering, we compute the spherical power\nspectrum and its covariance matrix and compare it to the standard\nthree-dimensional power spectrum to establish a connection. The spherical power\nspectrum recovers the three-dimensional power spectrum at each wavenumber k\nwith its angular dependence mu_k encoded in angular multipole l, and the\ncontributions of the line-of-sight projection to galaxy clustering such as the\ngravitational lensing effect can be readily accommodated in the spherical\nFourier analysis. A complete list of formulas for computing the relativistic\nspherical galaxy power spectrum is also presented.", "category": "astro-ph_CO" }, { "text": "PNe as observational constraints in chemical evolution models for NGC\n 6822: Chemical evolution models are useful for understanding the formation and\nevolution of stars and galaxies. Model predictions will be more robust as more\nobservational constraints are used. We present chemical evolution models for\nthe dwarf irregular galaxy NGC 6822 using chemical abundances of old and young\nPlanetary Nebulae (PNe) and \\ion{H}{ii} regions as observational constraints.\nTwo sets of chemical abundances, one derived from collisionally excited lines\n(CELs) and one, from recombination lines (RLs), are used. We try to use our\nmodels as a tool to discriminate between both procedures for abundance\ndeterminations. In our chemical evolution code, the chemical contribution of\nlow and intermediate mass stars is time delayed, while for the massive stars\nthe chemical contribution follows the instantaneous recycling approximation.\nOur models have two main free parameters: the mass-loss rate of a well-mixed\noutflow and the upper mass limit, $M_{up}$, of the initial mass function (IMF).\nTo reproduce the gaseous mass and the present-day O/H value we need to vary the\noutflow rate and the $M_{up}$ value.", "category": "astro-ph_CO" }, { "text": "Non-Gaussianity from false vacuum inflation: Old curvaton scenario: We calculate the three-point correlation function of the comoving curvature\nperturbation generated during an inflationary epoch driven by false vacuum\nenergy. We get a novel false vacuum shape bispectrum, which peaks in the\nequilateral limit. Using this result, we propose a scenario which we call \"old\ncurvaton\". The shape of the resulting bispectrum lies between the local and the\nfalse vacuum shapes. In addition we have a large running of the spectral index.", "category": "astro-ph_CO" }, { "text": "Utilizing Astroinformatics to Maximize the Science Return of the Next\n Generation Virgo Cluster Survey: The Next Generation Virgo Cluster Survey is a 104 square degree survey of the\nVirgo Cluster, carried out using the MegaPrime camera of the\nCanada-France-Hawaii telescope, from semesters 2009A-2012A. The survey will\nprovide coverage of this nearby dense environment in the universe to\nunprecedented depth, providing profound insights into galaxy formation and\nevolution, including definitive measurements of the properties of galaxies in a\ndense environment in the local universe, such as the luminosity function. The\nlimiting magnitude of the survey is g_AB = 25.7 (10 sigma point source), and\nthe 2 sigma surface brightness limit is g_AB ~ 29 mag arcsec^-2. The data\nvolume of the survey (approximately 50 terabytes of images), while large by\ncontemporary astronomical standards, is not intractable. This renders the\nsurvey amenable to the methods of astroinformatics. The enormous dynamic range\nof objects, from the giant elliptical galaxy M87 at M(B) = -21.6, to the\nfaintest dwarf ellipticals at M(B) ~ -6, combined with photometry in 5 broad\nbands (u* g' r' i' z'), and unprecedented depth revealing many previously\nunseen structures, creates new challenges in object detection and\nclassification. We present results from ongoing work on the survey, including\nphotometric redshifts, Virgo cluster membership, and the implementation of fast\ndata mining algorithms on the infrastructure of the Canadian Astronomy Data\nCentre, as part of the Canadian Advanced Network for Astronomical Research\n(CANFAR).", "category": "astro-ph_CO" }, { "text": "Steve: A hierarchical Bayesian model for Supernova Cosmology: We present a new Bayesian hierarchical model (BHM) named Steve for performing\ntype Ia supernova (SNIa) cosmology fits. This advances previous works by\nincluding an improved treatment of Malmquist bias, accounting for additional\nsources of systematic uncertainty, and increasing numerical efficiency. Given\nlight curve fit parameters, redshifts, and host-galaxy masses, we fit Steve\nsimultaneously for parameters describing cosmology, SNIa populations, and\nsystematic uncertainties. Selection effects are characterised using Monte-Carlo\nsimulations. We demonstrate its implementation by fitting realisations of SNIa\ndatasets where the SNIa model closely follows that used in Steve. Next, we\nvalidate on more realistic SNANA simulations of SNIa samples from the Dark\nEnergy Survey and low-redshift surveys. These simulated datasets contain more\nthan $60\\,000$ SNeIa, which we use to evaluate biases in the recovery of\ncosmological parameters, specifically the equation-of-state of dark energy,\n$w$. This is the most rigorous test of a BHM method applied to SNIa cosmology\nfitting, and reveals small $w$-biases that depend on the simulated SNIa\nproperties, in particular the intrinsic SNIa scatter model. This $w$-bias is\nless than $0.03$ on average, less than half the statistical uncertainty on\n$w$.These simulation test results are a concern for BHM cosmology fitting\napplications on large upcoming surveys, and therefore future development will\nfocus on minimising the sensitivity of Steve to the SNIa intrinsic scatter\nmodel.", "category": "astro-ph_CO" }, { "text": "A fast empirical method for galaxy shape measurements in weak lensing\n surveys: We describe a simple and fast method to correct ellipticity measurements of\ngalaxies from the distortion by the instrumental and atmospheric point spread\nfunction (PSF), in view of weak lensing shear measurements. The method performs\na classification of galaxies and associated PSFs according to measured shape\nparameters, and corrects the measured galaxy ellipticites by querying a large\nlookup table (LUT), built by supervised learning. We have applied this new\nmethod to the GREAT10 image analysis challenge, and present in this paper a\nrefined solution that obtains the competitive quality factor of Q = 104,\nwithout any shear power spectrum denoising or training. Of particular interest\nis the efficiency of the method, with a processing time below 3 ms per galaxy\non an ordinary CPU.", "category": "astro-ph_CO" }, { "text": "The Link Between the Hidden Broad Line Region and the Accretion Rate in\n Seyfert 2 Galaxies: In the past few years more and more pieces of evidence have been presented\nfor a revision of the widely accepted Unified Model of Active Galactic Nuclei.\nA model based solely on orientation cannot explain all the observed\nphenomenology. In the following, we will present evidence that accretion rate\nis also a key parameter for the presence of Hidden Broad Line Regions in\nSeyfert 2 galaxies. Our sample consists of 21 sources with polarized Hidden\nBroad Lines and 18 sources without Hidden Broad Lines. We use stellar velocity\ndispersions from several studies on the CaII and Mg b triplets in Seyfert 2\ngalaxies, to estimate the mass of the central black holes via the\nMbh-{\\sigma}\\ast relation. The ratio between the bolometric luminosity, derived\nfrom the intrinsic (i.e. unabsorbed) X-ray luminosity, and the Eddington\nluminosity is a measure of the rate at which matter accretes onto the central\nsupermassive black hole. A separation between Compton-thin HBLR and non-HBLR\nsources is clear, both in accretion rate (log Lbol/LEdd = -1.9) and in\nluminosity (log Lbol = 43.90). When, properly luminosity-corrected,\nCompton-thick sources are included, the separation between HBLR and non-HBLR is\nless sharp but no HBLR source falls below the Eddington ratio threshold. We\nspeculate that non-HBLR Compton-thick sources with accretion rate higher than\nthe threshold, do possess a BLR, but something, probably related to their heavy\nabsorption, is preventing us from observing it even in polarized light. Our\nresults for Compton-thin sources support theoretical expectations. In a model\npresented by Nicastro (2000), the presence of broad emission lines is\nintrinsically connected with disk instabilities occuring in proximity of a\ntransition radius, which is a function of the accretion rate, becoming smaller\nthan the innermost stable orbit for very low accretion rates and therefore\nluminosities.", "category": "astro-ph_CO" }, { "text": "IC10: the history of the nearest starburst galaxy through its Planetary\n Nebula and HII region populations: We report the results of spectroscopic observations, obtained with the Gemini\nNorth Multi-Object Spectrograph, of 9 planetary nebulae (PNe) and 15 \\hii\\\nregions located in the 5.5\\arcmin $\\times$5.5\\arcmin inner region of the nearby\nstarburst galaxy IC10. Twelve new candidate PNe have been discovered during our\npre-imaging phase. Nine of them have been spectroscopically confirmed. The\ndirect availability of the electron temperature diagnostics in several nebulae\nallowed an accurate determination of the metallicity map of IC10 at two epochs:\nthe present-time from \\hii regions and the old/intermediate-age from PNe. We\nfound a non-homogeneous distribution of metals at both epochs, but similar\naverage abundances were found for the two populations. The derived\nage-metallicity relation shows a little global enrichment interpreted as the\nloss of metals by SN winds and to differential gas outflows. Finally, we\nanalyzed the production of oxygen --through the third dredge-up-- in the\nchemical abundance patterns of the PN populations belonging to several dwarf\nirregular galaxies. We found that the third dredge-up of oxygen is a\nmetallicity dependent phenomenon occurring mainly for 12+$\\log$(O/H)$\\leq$7.7\nand substantially absent in IC10 PNe.", "category": "astro-ph_CO" }, { "text": "The role of Dark Matter sub-halos in the non-thermal emission of galaxy\n clusters: Annihilation of Dark Matter (DM) particles has been recognized as one of the\npossible mechanisms for the production of non-thermal particles and radiation\nin galaxy clusters. Previous studies have shown that, while DM models can\nreproduce the spectral properties of the radio halo in the Coma cluster, they\nfail in reproducing the shape of the radio halo surface brightness because they\nproduce a shape that is too concentrated towards the center of the cluster with\nrespect to the observed one. However, in previous studies the DM distribution\nwas modeled as a single spherically symmetric halo, while the DM distribution\nin Coma is found to have a complex and elongated shape. In this work we\ncalculate a range of non-thermal emissions in the Coma cluster by using the\nobserved distribution of DM sub-halos. We find that, by including the observed\nsub-halos in the DM model, we obtain a radio surface brightness with a shape\nsimilar to the observed one, and that the sub-halos boost the radio emission by\na factor between 5 and 20%, thus allowing to reduce the gap between the\nannihilation cross section required to reproduce the radio halo flux and the\nupper limits derived from other observations, and that this gap can be\nexplained by realistic values of the boosting factor due to smaller\nsubstructures. Models with neutralino mass of 9 GeV and composition $\\tau^+\n\\tau^-$, and mass of 43 GeV and composition $b \\bar b$ can fit the radio halo\nspectrum using the observed properties of the magnetic field in Coma, and do\nnot predict a gamma-ray emission in excess compared to the recent Fermi-LAT\nupper limits. These findings make these DM models viable candidate to explain\nthe origin of radio halos in galaxy clusters. [abridged]", "category": "astro-ph_CO" }, { "text": "Improved Cosmological Constraints from SDSS redMaPPer Clusters via X-ray\n Follow-up of a Complete Subsample of Systems: We improve upon the cosmological constraints derived from the abundance and\nweak-lensing data of redMaPPer clusters detected in the Sloan Digital Sky\nSurvey (SDSS). Specifically, we derive gas mass data using Chandra X-ray\nfollow-up of a complete sample of the 30 richest SDSS redMaPPer clusters with\n$z\\in[0.1,0.3]$, and use these additional data to improve upon the original\nanalysis by Costanzi et al. (2019b). We simultaneously fit for the parameters\nof the richness-mass relation, the cluster gas mass-mass relation, and\ncosmology. By including our X-ray cluster sample in the SDSS cluster cosmology\nanalysis, we measure $\\Omega_{\\rm m} = 0.25 \\pm 0.04$ and $\\sigma_8 =\n0.85^{+0.06}_{-0.08}$. These constraints represent a 25.5% and 29.8% reduction\nin the size of the 68% confidence intervals of $\\Omega_{\\rm m}$ and $\\sigma_8$\nrespectively, relative to the constraints published in Costanzi et al. (2019b).\nOur cosmological constraints are in agreement with early universe results from\nPlanck. As a byproduct of our analysis, we also perform an independent\ncalibration of the amplitude of the $\\langle M_{\\rm gas}^{\\rm true}|M_{\\rm\n500c}\\rangle$ scaling relation. Our calibration is consistent with and of\ncomparable precision to that of Mantz et al. (2016b).", "category": "astro-ph_CO" }, { "text": "The zCOSMOS 20k Group Catalog: We present an optical group catalog between 0.1 < z < 1 based on 16,500\nhigh-quality spectroscopic redshifts in the completed zCOSMOS-bright survey.\nThe catalog published herein contains 1498 groups in total and 192 groups with\nmore than five observed members. The catalog includes both group properties and\nthe identification of the member galaxies. Based on mock catalogs, the\ncompleteness and purity of groups with three and more members should be both\nabout 83% with respect to all groups that should have been detectable within\nthe survey, and more than 75% of the groups should exhibit a one-to-one\ncorrespondence to the \"real\" groups. Particularly at high redshift, there are\napparently more galaxies in groups in the COSMOS field than expected from mock\ncatalogs. We detect clear evidence for the growth of cosmic structure over the\nlast seven billion years in the sense that the fraction of galaxies that are\nfound in groups (in volume-limited samples) increases significantly with cosmic\ntime. In the second part of the paper, we develop a method for associating\ngalaxies that only have photo-z to our spectroscopically identified groups. We\nshow that this leads to improved definition of group centers, improved\nidentification of the most massive galaxies in the groups, and improved\nidentification of central and satellite galaxies, where we define the former to\nbe galaxies at the minimum of the gravitational potential wells. Subsamples of\ncentrals and satellites in the groups can be defined with purities up to 80%,\nwhile a straight binary classification of all group and non-group galaxies into\ncentrals and satellites achieves purities of 85% and 75%, respectively, for the\nspectroscopic sample.", "category": "astro-ph_CO" }, { "text": "An exploration of an early gravity transition in light of cosmological\n tensions: We study a step-like transition in the value of the effective Planck mass (or\neffective gravitational constant) on cosmological scales prior to\nrecombination. We employ CMB, BAO, and SNIa data and find they are sufficient\nto strongly constrain our implementation of the Effective Field Theory of Dark\nEnergy and Modified Gravity, used to model the transition, to a limited\nparameter space. The data prefer a $\\sim 5\\%$ shift in the value of the\neffective Planck mass ($<10 \\%$ at $2 \\sigma$) prior to recombination. This\nTransitional Planck Mass (TPM) model is free to undergo its transition at any\npoint over multiple decades of scale factor prior to recombination,\n$\\log_{10}(a) = -5.32^{+0.96}_{-0.72}$ (68\\% CL). This lowers the sound horizon\nat last scattering, which increases the Hubble constant to $71.09 \\pm 0.75$ km\n$\\textrm{s}^{-1}\\textrm{Mpc}^{-1}$ with a combination of local measurements as\nprior and to $69.22^{+0.67}_{-0.86}$ km $\\textrm{s}^{-1}\\textrm{Mpc}^{-1}$ when\nthe prior is excluded. The TPM model improves $\\chi^2$ with respect to\n$\\Lambda$CDM by $\\Delta \\chi^2 = -23.72$ with the $H_0$ prior and $\\Delta\n\\chi^2 = -4.8$ without the prior. The model allows for both $H_0 > 70$\nkm$\\textrm{s}^{-1}\\textrm{Mpc}^{-1}$ and $S_8 < 0.80$ simultaneously with lower\nvalues of $S_8$ due to a reduction in the matter density $\\Omega_m$ to offset\nthe increase in $H_0$ relative to $\\Lambda$CDM. While this is a particular\nmodified gravity model, studying other variants of modified gravity may be a\nproductive path for potentially resolving cosmological tensions, while avoiding\nthe need for a cosmological constant.", "category": "astro-ph_CO" }, { "text": "Is the misalignment of the Local Group velocity and the 2MASS Redshift\n Survey dipole typical in a LambdaCDM model?: We predict the acceleration of the Local Group generated by the 2MASS\nRedshift Survey within the framework of LambdaCDM and the halo model of\ngalaxies. We show that as the galaxy fluctuations derived from the halo model\nhave more power on small scales compared with the mass fluctuations, the\nmisalignment angle between the CMB velocity vector and the 2MRS dipole is in\nreasonable agreement with the observed 21 degrees. This statistical analysis\nsuggests that it is not necessary to invoke a hypothetical nearby galaxy or a\ndistant cluster to explain this misalignment.", "category": "astro-ph_CO" }, { "text": "Instability in axion inflation with strong backreaction from gauge modes: We perform an analytical study of the stability of the background solution of\nthe model in which an inflaton, through an axionic coupling to a $U(1)$ gauge\nfield, causes an amplification of the gauge field modes that strongly backreact\non its dynamics. To this goal, we study the evolution of the gauge field modes\ncoupled to the inflaton zero mode, treating perturbatively the deviation of the\ninflaton velocity from its mean-field value. As long as the system is in the\nstrong backreaction regime we find that the inflaton velocity performs\noscillations of increasing amplitude about the value it would have in the\napproximation of constant velocity, confirming an instability that has been\nobserved in numerical studies.", "category": "astro-ph_CO" }, { "text": "Testable dark energy predictions from current data: Given a class of dark energy models, constraints from one set of cosmic\nacceleration observables make predictions for other observables. Here we\npresent the allowed ranges for the expansion rate H(z), distances D(z), and the\nlinear growth function G(z) (as well as other, derived growth observables) from\nthe current combination of cosmological measurements of supernovae, the cosmic\nmicrowave background, baryon acoustic oscillations, and the Hubble constant.\nWith a cosmological constant as the dark energy and assuming near-minimal\nneutrino masses, the growth function is already predicted to better than 2%\nprecision at any redshift, with or without spatial curvature. Direct\nmeasurements of growth that match this precision offer the opportunity to\nstringently test and potentially rule out a cosmological constant. While\npredictions in the broader class of quintessence models are weaker, it is\nremarkable that they are typically within a factor of 2-3 of forecasts for\nfuture space-based supernovae and Planck CMB measurements. In particular,\nmeasurements of growth at any redshift, or the Hubble constant H_0, that exceed\nLambdaCDM predictions by substantially more than 2% would rule out not only a\ncosmological constant but also the whole quintessence class, with or without\ncurvature and early dark energy. Barring additional systematic errors hiding in\nthe data, such a discovery would require more exotic explanations of cosmic\nacceleration such as phantom dark energy, dark energy clustering, or\nmodifications of gravity.", "category": "astro-ph_CO" }, { "text": "Probing Parity Violation in the Stochastic Gravitational Wave Background\n with Astrometry: Astrometry holds the potential for testing fundamental physics through the\neffects of the Stochastic Gravitational Wave Background (SGWB) in the $\\sim\n1-100$ nHz frequency band on precision measurements of stellar positions. Such\nmeasurements are complementary to tests made possible by the detection of the\nSGWB using Pulsar Timing Arrays. Here, the feasibility of using astrometry for\nthe identification of parity-violating signals within the SGWB is investigated.\nThis is achieved by defining and quantifying a non-vanishing $EB$ correlation\nfunction within astrometric correlation functions, and investigating how one\nmight estimate the detectability of such signals.", "category": "astro-ph_CO" }, { "text": "Probing the anisotropic expansion history of the universe with cosmic\n microwave background: We propose a simple technique to detect any anisotropic expansion stage in\nthe history of the universe starting from the inflationary stage to the surface\nof last scattering from the CMBR data. We use the property that any anisotropic\nexpansion in the universe would deform the shapes of the primordial density\nperturbations and this deformation can be detected in a shape analysis of\nsuperhorizon fluctuations in CMBR. Using this analysis we obtain the constraint\non any previous anisotropic expansion of the universe to be less than about\n35%.", "category": "astro-ph_CO" }, { "text": "Absence of concordance in a simple self-interacting neutrino cosmology: Some cosmic microwave background (CMB) data allow a cosmological scenario in\nwhich the free streaming of neutrinos is delayed until close to\nmatter-radiation equality. Interestingly, recent analyses have revealed that\nlarge-scale structure (LSS) data also align with this scenario, discarding the\npossibility of an accidental feature in the CMB sky and calling for further\ninvestigation into the free-streaming nature of neutrinos. By assuming a simple\nrepresentation of self-interacting neutrinos, we investigate whether this\nnonstandard scenario can accommodate a consistent cosmology for both the CMB\npower spectra and the large-scale distribution of galaxies simultaneously.\nEmploying three different approaches - a profile likelihood exploration, a\nnested sampling method, and a heuristic Metropolis-Hasting approximation - we\nexhaustively explore the parameter space and demonstrate that galaxy data\nexacerbates the challenge already posed by the Planck polarization data for\nthis nonstandard scenario. We find that the most conservative value of the\nBayes factor disfavors the interactions among neutrinos over a $\\Lambda$CDM +\n$N_\\mathrm{eff}$ + $\\sum m_\\nu$ model with odds of $23:1000$ and that the\ndifficulty of simultaneously fitting the galaxy and CMB data relates to the\nso-called $S_8$ discrepancy. Our analysis not only emphasizes the need to\nconsider a broader range of phenomenologies in the early Universe but also\nhighlights significant numerical and theoretical challenges ahead in uncovering\nthe exact nature of the feature observed in the data or, ultimately, confirming\nthe standard chronological evolution of the Universe.", "category": "astro-ph_CO" }, { "text": "The role of Dark Matter sub-halos in the non-thermal emission of galaxy\n clusters: Annihilation of Dark Matter (DM) particles has been recognized as one of the\npossible mechanisms for the production of non-thermal particles and radiation\nin galaxy clusters. Previous studies have shown that, while DM models can\nreproduce the spectral properties of the radio halo in the Coma cluster, they\nfail in reproducing the shape of the radio halo surface brightness because they\nproduce a shape that is too concentrated towards the center of the cluster with\nrespect to the observed one. However, in previous studies the DM distribution\nwas modeled as a single spherically symmetric halo, while the DM distribution\nin Coma is found to have a complex and elongated shape. In this work we\ncalculate a range of non-thermal emissions in the Coma cluster by using the\nobserved distribution of DM sub-halos. We find that, by including the observed\nsub-halos in the DM model, we obtain a radio surface brightness with a shape\nsimilar to the observed one, and that the sub-halos boost the radio emission by\na factor between 5 and 20%, thus allowing to reduce the gap between the\nannihilation cross section required to reproduce the radio halo flux and the\nupper limits derived from other observations, and that this gap can be\nexplained by realistic values of the boosting factor due to smaller\nsubstructures. Models with neutralino mass of 9 GeV and composition $\\tau^+\n\\tau^-$, and mass of 43 GeV and composition $b \\bar b$ can fit the radio halo\nspectrum using the observed properties of the magnetic field in Coma, and do\nnot predict a gamma-ray emission in excess compared to the recent Fermi-LAT\nupper limits. These findings make these DM models viable candidate to explain\nthe origin of radio halos in galaxy clusters. [abridged]", "category": "astro-ph_CO" }, { "text": "All sky angular power spectrum: I. Estimating brightness temperature\n fluctuations using TGSS 150 MHz survey: Measurements of the Galactic synchrotron emission is relevant for the 21-cm\nstudies from the Epoch of Reionization. The study of the synchrotron emission\nis also useful to quantify the fluctuations in the magnetic field and the\ncosmic ray electron density of the turbulent interstellar medium (ISM) of our\nGalaxy. Here, we present the all-sky angular power spectrum $(C_{\\ell})$\nmeasurements of the diffuse synchrotron emission using the TIFR GMRT Sky Survey\n(TGSS) at 150 {\\rm MHz}. We estimate $C_{\\ell}$ using visibility data both\nbefore and after subtracting the modelled point sources. The amplitude of the\nmeasured $C_{\\ell}$ falls significantly after subtracting the point sources,\nand it is also slightly higher in the Galactic plane for the residual data. The\nresidual $C_{\\ell}$ is most likely to be dominated by the Galactic synchrotron\nemission. The amplitude of the residual $C_{\\ell}$ falls significantly away\nfrom the Galactic plane. We find the measurements are quite symmetric in the\nNorthern and Southern hemispheres except in the latitude range $15-30^{\\circ}$\nwhich is the transition region from the disk dominated to diffuse halo\ndominated region. The comparison between this interferometric measurement with\nthe scaled version of the Haslam rms map at 150 {\\rm MHz} shows that the\ncorrelation coefficient $(r)$ is more than 0.5 for most of the latitude ranges\nconsidered here. This signifies the TGSS survey is quite sensitive to the\ndiffuse Galactic synchrotron radiation.", "category": "astro-ph_CO" }, { "text": "G\u00f6del-type universes and chronology protection in Horava-Lifshitz\n gravity: In the attempts toward a quantum gravity theory, general relativity faces a\nserious difficulty since it is non-renormalizable theory. Ho\\v{r}ava-Lifshitz\ngravity offers a framework to circumvent this difficulty, by sacrificing the\nlocal Lorentz invariance at ultra-high energy scales in exchange of\npower-counting renormalizability. The Lorentz symmetry is expected to be\nrecovered at low and medium energy scales. If gravitation is to be described by\na Ho\\v{r}ava-Lifshitz gravity theory there are a number of issues that ought to\nbe reexamined in its context, including the question as to whether this gravity\nincorporates a chronology protection, or particularly if it allows G\\\"odel-type\nsolutions with violation of causality. We show that Ho\\v{r}ava-Lifshitz gravity\nonly allows hyperbolic G\\\"odel-type space-times whose essential parameters $m$\nand $\\omega$ are in the chronology respecting intervals, excluding therefore\nany noncausal G\\\"odel-type space-times in the hyperbolic class. There emerges\nfrom our results that the famous noncausal G\\\"odel model is not allowed in\nHo\\v{r}ava-Lifshitz gravity. The question as to whether this quantum gravity\ntheory permits hyperbolic G\\\"odel-type solutions in the chronology preserving\ninterval of the essential parameters is also examined. We show that\nHo\\v{r}ava-Lifshitz gravity not only excludes the noncausal G\\\"odel universe,\nbut also rules out any hyperbolic G\\\"odel-type solutions for physically\nwell-motivated perfect-fluid matter content.", "category": "astro-ph_CO" }, { "text": "A Bayesian analysis of redshifted 21-cm HI signal and foregrounds:\n Simulations for LOFAR: Observations of the EoR with the 21-cm hyperfine emission of neutral hydrogen\n(HI) promise to open an entirely new window onto the formation of the first\nstars, galaxies and accreting black holes. In order to characterize the weak\n21-cm signal, we need to develop imaging techniques which can reconstruct the\nextended emission very precisely. Here, we present an inversion technique for\nLOFAR baselines at NCP, based on a Bayesian formalism with optimal spatial\nregularization, which is used to reconstruct the diffuse foreground map\ndirectly from the simulated visibility data. We notice the spatial\nregularization de-noises the images to a large extent, allowing one to recover\nthe 21-cm power-spectrum over a considerable $k_{\\perp}-k_{\\para}$ space in the\nrange of $0.03\\,{\\rm Mpc^{-1}}/(1+z)>=0.29) than is seen in non-infrared selected samples, likely\ndue to enhanced star formation rates and dust obscuration in infrared-selected\ngalaxies. We estimate that the vast majority (72-83%) of z<2 Herschel-selected\ngalaxies would drop out of traditional submillimeter surveys at 0.85-1mm. We\nestimate the luminosity function and implied star-formation rate density\ncontribution of HSGs at z<1.6 and find overall agreement with work based on\n24um extrapolations of the LIRG, ULIRG and total infrared contributions. This\nwork significantly increased the number of spectroscopically confirmed\ninfrared-luminous galaxies at z>>0 and demonstrates the growing importance of\ndusty starbursts for galaxy evolution studies and the build-up of stellar mass\nthroughout cosmic time. [abridged]", "category": "astro-ph_CO" }, { "text": "A new gravitational N-body simulation algorithm for investigation of\n cosmological chaotic advection: Recently alternative approaches in cosmology seeks to explain the nature of\ndark matter as a direct result of the non-linear spacetime curvature due to\ndifferent types of deformation potentials. In this context, a key test for this\nhypothesis is to examine the effects of deformation on the evolution of large\nscales structures. An important requirement for the fine analysis of this pure\ngravitational signature (without dark matter elements) is to characterize the\nposition of a galaxy during its trajectory to the gravitational collapse of\nsuper clusters at low redshifts. In this context, each element in an\ngravitational N-body simulation behaves as a tracer of collapse governed by the\nprocess known as chaotic advection (or lagrangian turbulence). In order to\ndevelop a detailed study of this new approach we develop the COsmic LAgrangian\nTUrbulence Simulator (COLATUS) to perform gravitational N-body simulations\nbased on Compute Unified Device Architecture (CUDA) for graphics processing\nunits (GPUs). In this paper we report the first robust results obtained from\nCOLATUS.", "category": "astro-ph_CO" }, { "text": "The evolution of galaxy intrinsic alignments in the MassiveBlack II\n universe: We investigate the redshift evolution of the intrinsic alignments (IA) of\ngalaxies in the \\texttt{MassiveBlackII} (MBII) simulation. We select galaxy\nsamples above fixed subhalo mass cuts ($M_h>10^{11,12,13}~M_{\\odot}/h$) at\n$z=0.6$ and trace their progenitors to $z=3$ along their merger trees. Dark\nmatter components of $z=0.6$ galaxies are more spherical than their progenitors\nwhile stellar matter components tend to be less spherical than their\nprogenitors. The distribution of the galaxy-subhalo misalignment angle peaks at\n$\\sim10~\\mathrm{deg}$ with a mild increase with time. The evolution of the\nellipticity-direction~(ED) correlation amplitude $\\omega(r)$ of galaxies (which\nquantifies the tendency of galaxies to preferentially point towards surrounding\nmatter overdensities) is governed by the evolution in the alignment of\nunderlying dark matter~(DM) subhaloes to the matter density of field, as well\nas the alignment between galaxies and their DM subhaloes. At scales\n$\\sim1~\\mathrm{cMpc}/h$, the alignment between DM subhaloes and matter\noverdensity gets suppressed with time, whereas the alignment between galaxies\nand DM subhaloes is enhanced. These competing tendencies lead to a complex\nredshift evolution of $\\omega(r)$ for galaxies at $\\sim1~\\mathrm{cMpc}/h$. At\nscales $>1~\\mathrm{cMpc}/h$, alignment between DM subhaloes and matter\noverdensity does not evolve significantly; the evolution of the galaxy-subhalo\nmisalignment therefore leads to an increase in $\\omega(r)$ for galaxies by a\nfactor of $\\sim4$ from $z=3$ to $0.6$ at scales $>1~\\mathrm{cMpc}/h$. The\nbalance between competing physical effects is scale dependant, leading to\ndifferent conclusions at much smaller scales($\\sim0.1~\\mathrm{Mpc}/h$).", "category": "astro-ph_CO" }, { "text": "The (black hole mass)-(host spheroid luminosity) relation at high and\n low masses, the quadratic growth of black holes, and intermediate-mass black\n hole candidates: From a sample of 72 galaxies with reliable supermassive black hole masses\nM_(bh), we derive the M_(bh)-(host spheroid luminosity, L) relation for (i) the\nsubsample of 24 core-Sersic galaxies with partially depleted cores, and (ii)\nthe remaining subsample of 48 Sersic galaxies. Using (K_s)-band 2MASS data, we\nfind the near-linear relation M_(bh) ~ L_(K_s)^(1.10+/-0.20) for the\ncore-Sersic spheroids thought to be built in additive dry merger events, while\nM_(bh) ~ L_(K_s)^(2.73+/-0.55) for the Sersic spheroids built from gas-rich\nprocesses. After converting literature B-band disk galaxy magnitudes into\ninclination- and dust-corrected bulge magnitudes, via a useful new equation\npresented herein, we obtain a similar result. Unlike with the M_(bh)-sigma\ndiagram, which is also updated here using the same galaxy sample, it remains\nunknown whether barred and non-barred Sersic galaxies are offset from each\nother in the M_(bh)-L diagram.\n While black hole feedback has typically been invoked to explain what was\npreviously thought to be a nearly constant M_bh/M_sph mass ratio of ~0.2%, we\nadvocate that the near-linear M_bh-L and M_bh-M_sph relations observed at high\nmasses may have instead largely arisen from the additive dry merging of\ngalaxies. We argue that feedback results in a dramatically different scaling\nrelation, such that black hole mass scales roughly quadratically with the\nspheroid mass in Sersic galaxies. We therefore introduce a revised cold-gas\n'quasar' mode feeding equation for semi-analytical models to reflect what we\ndub the \"quadratic growth\" of black holes in Sersic galaxies built amidst\ngas-rich processes. Finally, we use our new Sersic M_bh-L equations to predict\nthe masses of candidate `intermediate mass' black holes in almost 50 low\nluminosity spheroids containing AGN, finding many masses between that of\nstellar mass black holes and supermassive black holes.", "category": "astro-ph_CO" }, { "text": "The eROSITA Final Equatorial-Depth Survey (eFEDS): Characterization of\n Morphological Properties of Galaxy Groups and Clusters: Understanding the cluster population of clusters of galaxies is of the utmost\nimportance for using cluster samples in both astrophysical and cosmological\nstudies. We present an in-depth analysis of the X-ray morphological parameters\nof the galaxy clusters and groups detected in the eROSITA Final\nEquatorial-Depth Survey (eFEDS). We study the eROSITA X-ray imaging data for a\nsample of 325 clusters and groups that are significantly detected in the eFEDS\nfield. We characterize their dynamical properties by measuring a number of\ndynamical estimators: concentration, central density, cuspiness, ellipticity,\npower-ratios, photon asymmetry, and Gini coefficient. The galaxy clusters and\ngroups detected in eFEDS, covering a luminosity range of more than three orders\nof magnitude and large redshift range out to 1.2 provide an ideal sample for\nstudying the redshift and luminosity evolution of the morphological parameters\nand characterization of the underlying dynamical state of the sample. Based on\nthese measurements we construct a new dynamical indicator, relaxation score,\nfor all the clusters in the sample. We find no evidence for bimodality in the\ndistribution of morphological parameters of our clusters, rather we observe a\nsmooth transition from the cool-core to non-cool-core and from relaxed to\ndisturbed states. A significant evolution in redshift and luminosity is also\nobserved in the morphological parameters examined in this study after carefully\ntaking into account the selection effects. We determine that our eFEDS-selected\ncluster sample, differently than ROSAT-based cluster samples, is not biased\ntoward relaxed clusters, but contains a similar fraction of disturbed as SZ\nsurveys.", "category": "astro-ph_CO" }, { "text": "Relativistic and non-Gaussianity contributions to the one-loop power\n spectrum: We compute the one-loop density power spectrum including Newtonian and\nrelativistic contributions, as well as the primordial non-Gaussianity\ncontributions from $f_{\\rm NL}$ and $g_{\\rm NL}$ in the local configuration. To\nthis end we take solutions to the Einstein equations in the long-wavelength\napproximation and provide expressions for the matter density perturbation at\nsecond and third order. These solutions have shown to be complementary to the\nusual Newtonian cosmological perturbations. We confirm a sub-dominant effect\nfrom pure relativistic terms, manifested at scales dominated by cosmic\nvariance, but find that a sizable effect of order one comes from $g_{\\rm NL}$\nvalues allowed by Planck-2018 constraints, manifested at scales probed by\nforthcoming galaxy surveys like DESI and Euclid. As a complement, we present\nthe matter bispectrum at the tree-level including the mentioned contributions.", "category": "astro-ph_CO" }, { "text": "Hunting WIMPs with LISA: Correlating dark matter and gravitational wave\n signals: The thermal freeze-out mechanism in its classical form is tightly connected\nto physics beyond the Standard Model around the electroweak scale, which has\nbeen the target of enormous experimental efforts. In this work we study a dark\nmatter model in which freeze-out is triggered by a strong first-order phase\ntransition in a dark sector, and show that this phase transition must also\nhappen close to the electroweak scale, i.e. in the temperature range relevant\nfor gravitational wave searches with the LISA mission. Specifically, we\nconsider the spontaneous breaking of a $U(1)^\\prime$ gauge symmetry through the\nvacuum expectation value of a scalar field, which generates the mass of a\nfermionic dark matter candidate that subsequently annihilates into dark Higgs\nand gauge bosons. In this set-up the peak frequency of the gravitational wave\nbackground is tightly correlated with the dark matter relic abundance, and\nimposing the observed value for the latter implies that the former must lie in\nthe milli-Hertz range. A peculiar feature of our set-up is that the dark sector\nis not necessarily in thermal equilibrium with the Standard Model during the\nphase transition, and hence the temperatures of the two sectors evolve\nindependently. Nevertheless, the requirement that the universe does not enter\nan extended period of matter domination after the phase transition, which would\nstrongly dilute any gravitational wave signal, places a lower bound on the\nportal coupling that governs the entropy transfer between the two sectors. As a\nresult, the predictions for the peak frequency of gravitational waves in the\nLISA band are robust, while the amplitude can change depending on the initial\ndark sector temperature.", "category": "astro-ph_CO" }, { "text": "Intrinsic Shapes of Very Flat Elliptical Galaxies: Photometric data from the literature is combined with triaxial mass models to\nderive variation in the intrinsic shapes of the light distribution of\nelliptical galaxies NGC 720, 2768 and 3605. The inferred shape variation in\ngiven by a Bayesian probability distribution, assuming a uniform prior. The\nlikelihood of obtaining the data is calculated by using ensemble of triaxial\nmodels. We apply the method to infer the shape variation of a galaxy, using the\nellipticities and the difference in the position angles at two suitably chosen\npoints from the profiles of the photometric data. Best constrained shape\nparameters are found to be the short to long axial ratios at small and large\nradii, and the absolute values of the triaxiallity difference between these\nradii.", "category": "astro-ph_CO" }, { "text": "Inflationary tensor fossils in large-scale structure: Inflation models make specific predictions for a tensor-scalar-scalar\nthree-point correlation, or bispectrum, between one gravitational-wave (tensor)\nmode and two density-perturbation (scalar) modes. This tensor-scalar-scalar\ncorrelation leads to a local power quadrupole, an apparent departure from\nstatistical isotropy in our Universe, as well as characteristic four-point\ncorrelations in the current mass distribution in the Universe. So far, the\npredictions for these observables have been worked out only for single-clock\nmodels in which certain consistency conditions between the tensor-scalar-scalar\ncorrelation and tensor and scalar power spectra are satisfied. Here we review\nthe requirements on inflation models for these consistency conditions to be\nsatisfied. We then consider several examples of inflation models, such as\nnon-attractor and solid inflation models, in which these conditions are put to\nthe test. In solid inflation the simplest consistency conditions are already\nviolated whilst in the non-attractor model we find that, contrary to the\nstandard scenario, the tensor-scalar-scalar correlator probes directly relevant\nmodel-dependent information. We work out the predictions for observables in\nthese models. For non-attractor inflation we find an apparent local quadrupolar\ndeparture from statistical isotropy in large-scale structure but that this\npower quadrupole decreases very rapidly at smaller scales. The consistency of\nthe CMB quadrupole with statistical isotropy then constrains the distance scale\nthat corresponds to the transition from the non-attractor to attractor phase of\ninflation to be larger than the currently observable horizon. Solid inflation\npredicts clustering fossils signatures in the current galaxy distribution that\nmay be large enough to be detectable with forthcoming, and possibly even\ncurrent, galaxy surveys.", "category": "astro-ph_CO" }, { "text": "The 6x2pt method: supernova velocities meet multiple tracers: We present a new methodology to analyse in a comprehensive way large-scale\nand supernovae (or any other distance indicator) surveys. Our approach combines\ngalaxy and supernova position and redshift data with supernova peculiar\nvelocities, obtained through their magnitude scatter, to construct a 6x2pt\nanalysis which includes six power spectra. The 3x3 correlation matrix of these\nspectra expresses exhaustively the information content of the surveys at the\nlinear level. We proceed then to forecast the performance of future surveys\nlike LSST and 4MOST with a Fisher Matrix analysis, adopting both a\nmodel-dependent and a model-independent approach. We compare the performance of\nthe 6x2pt approach to the traditional one using only galaxy clustering and some\nrecently proposed combinations of galaxy and supernovae data and quantify the\npossible gains by optimally extracting the linear information. We show that the\n6x2pt method shrinks the uncertainty area in the $\\sigma_8, \\gamma$ plane by\nmore than half when compared to the traditional method. The combined clustering\nand velocity data on the growth of structures has uncertainties at similar\nlevels to those of the CMB but exhibit orthogonal degeneracies, and the\ncombined constraints yield improvements of factors of 5 in each of the five\ncosmological parameters here considered. Concerning the model-independent\nresults, we find that our method can improve the constraints on $H(z)/H_0$ in\nall redshift bins by more than 70% with respect to the galaxy clustering alone\nand by 30% when supernova velocities (but not clustering) are considered,\nreaching a precision of 3-4% at high redshifts.", "category": "astro-ph_CO" }, { "text": "Evidence for Three Accreting Black Holes in a Galaxy at z~1.35: A\n Snapshot of Recently Formed Black Hole Seeds?: One of the key open questions in cosmology today pertains to understanding\nwhen, where and how super massive black holes form, while it is clear that\nmergers likely play a significant role in the growth cycles of black holes, how\nsupermassive black holes form, and how galaxies grow around them. Here, we\npresent Hubble Space Telescope WFC3/IR grism observations of a clumpy galaxy at\nz=1.35, with evidence for 10^6 - 10^7 Msun rapidly growing black holes in\nseparate sub-components of the host galaxy. These black holes could have been\nbrought into close proximity as a consequence of a rare multiple galaxy merger\nor they could have formed in situ. Such holes would eventually merge into a\ncentral black hole as the stellar clumps/components presumably coalesce to form\na galaxy bulge. If we are witnessing the in-situ formation of multiple black\nholes, their properties can inform seed formation models and raise the\npossibility that massive black holes can continue to emerge in star-forming\ngalaxies as late as z=1.35 (4.8 Gyr after the Big Bang).", "category": "astro-ph_CO" }, { "text": "Contamination of the Epoch of Reionization power spectrum in the\n presence of foregrounds: We construct foreground simulations comprising spatially correlated\nextragalactic and diffuse Galactic emission components and calculate the\n`intrinsic' (instrument-free) two-dimensional spatial power spectrum and the\ncylindrically and spherically averaged three-dimensional k-space power spectra\nof the Epoch of Reionization (EoR) and our foreground simulations using a\nBayesian power spectral estimation framework. This leads us to identify a model\ndependent region of optimal signal estimation for our foreground and EoR\nmodels, within which the spatial power in the EoR signal relative to\nforegrounds is maximised. We identify a target field dependent region, in\nk-space, of intrinsic foreground power spectral contamination at low k_perp and\nk_parallel and a transition to a relatively foreground-free intrinsic EoR\nwindow in the complement to this region. The contaminated region of k-space\ndemonstrates that simultaneous estimation of the EoR and foregrounds is\nimportant for obtaining statistically robust estimates of the EoR power\nspectrum; biased results will be obtained from methodologies that ignore their\ncovariance. Using simulated observations with frequency dependent uv-coverage\nand primary beam, with the former derived for HERA in 37-antenna and\n331-antenna configuration, we recover instrumental power spectra consistent\nwith their intrinsic counterparts. We discuss the implications of these results\nfor optimal strategies for unbiased estimation of the EoR power spectrum.", "category": "astro-ph_CO" }, { "text": "Induced Gravity and the Attractor Dynamics of Dark Energy/Dark Matter: Attractor solutions that give dynamical reasons for dark energy to act like\nthe cosmological constant, or behavior close to it, are interesting\npossibilities to explain cosmic acceleration. Coupling the scalar field to\nmatter or to gravity enlarges the dynamical behavior; we consider both\ncouplings together, which can ameliorate some problems for each individually.\nSuch theories have also been proposed in a Higgs-like fashion to induce gravity\nand unify dark energy and dark matter origins. We explore restrictions on such\ntheories due to their dynamical behavior compared to observations of the cosmic\nexpansion. Quartic potentials in particular have viable stability properties\nand asymptotically approach general relativity.", "category": "astro-ph_CO" }, { "text": "A Survey of z~6 Quasars in the SDSS Deep Stripe. II. Discovery of Six\n Quasars at z_{AB}>21: We present the discovery of six new quasars at z~6 selected from the Sloan\nDigital Sky Survey (SDSS) southern survey, a deep imaging survey obtained by\nrepeatedly scanning a stripe along the celestial equator. The six quasars are\nabout two magnitudes fainter than the luminous z~6 quasars found in the SDSS\nmain survey and one magnitude fainter than the quasars reported in Paper I\n(Jiang et al. 2008). Four of them comprise a complete flux-limited sample at\n21$7 quasars may therefore be needed to establish a clearer picture\nof the IGM neutral fraction at these redshifts.", "category": "astro-ph_CO" }, { "text": "The Effect of Modified Gravity on the Odds of the Bound Violations of\n the Turn-Around Radii: The turn-around radii of the galaxy groups show the imprint of a long battle\nbetween their self-gravitational forces and the accelerating space. The\nstandard $\\Lambda$CDM cosmology based on the general relativity (GR) predicts\nthe existence of an upper bound on the expectation value of the turn-around\nradius which is rarely violated by individual galaxy groups. We speculate that\na deviation of the gravitational law from GR on the cosmological scale could\ncause an appreciable shift of the mean turn-around radius to higher values and\nmake the occurrence of the bound violation more probable. Analyzing the data\nfrom high-resolution N-body simulations for two specific models with modified\ngravity (MG) and the standard GR+$\\Lambda$CDM cosmology, we determine the\nturn-around radii of the massive Rockstar groups from the peculiar motions of\nthe galactic halos located in the bound zone where the fifth force generated by\nMG is expected to be at most partially shielded. We detect a $4\\sigma$ signal\nof difference in the odds of the bound violations between a fiducial MG and the\nGR models, proving that the odds of the bound violations increase with the\nstrength of the fifth force produced by the presence of MG. The advantage of\nusing the odds of the bound violations as a complementary diagnostics to probe\nthe nature of gravity is discussed.", "category": "astro-ph_CO" }, { "text": "Constraining the mass of light bosonic dark matter using SDSS\n Lyman-$\u03b1$ forest: If a significant fraction of the dark matter in the Universe is made of an\nultra-light scalar field, named fuzzy dark matter (FDM) with a mass $m_a$ of\nthe order of $10^{-22}-10^{-21}$ eV, then its de Broglie wavelength is large\nenough to impact the physics of large scale structure formation. In particular,\nthe associated cut-off in the linear matter power spectrum modifies the\nstructure of the intergalactic medium (IGM) at the scales probed by the\nLyman-$\\alpha$ forest of distant quasars. We study this effect by making use of\ndedicated cosmological simulations which take into account the hydrodynamics of\nthe IGM. We explore heuristically the amplitude of quantum pressure for the FDM\nmasses considered here and conclude that quantum effects should not modify\nsignificantly the non-linear evolution of matter density at the scales relevant\nto the measured Lyman-$\\alpha$ flux power, and for $m_a \\geq 10^{-22}$ eV. We\nderive a scaling law between $m_a$ and the mass of the well-studied thermal\nwarm dark matter (WDM) model that is best adapted to the Lyman-$\\alpha$ forest\ndata, and differs significantly from the one infered by a simple linear\nextrapolation. By comparing FDM simulations with the Lyman-$\\alpha$ flux power\nspectra determined from the BOSS survey, and marginalizing over relevant\nnuisance parameters, we exclude FDM masses in the range $10^{-22} \\leq m_a <\n2.3\\times 10^{-21}$ eV at 95 % CL. Adding higher-resolution Lyman-$\\alpha$\nspectra extends the exclusion range up to $2.9\\times 10^{-21}$ eV. This\nprovides a significant constraint on FDM models tailored to solve the\n\"small-scale problems\" of $\\Lambda$CDM.", "category": "astro-ph_CO" }, { "text": "Redshift-weighted constraints on primordial non-Gaussianity from the\n clustering of the eBOSS DR14 quasars in Fourier space: We present constraints on local primordial non-Gaussianity (PNG),\nparametrized through $f^{\\rm loc}_{\\rm NL}$, using the Sloan Digital Sky Survey\nIV extended Baryon Oscillation Spectroscopic Survey Data Release 14 quasar\nsample. We measure and analyze the anisotropic clustering of the quasars in\nFourier space, testing for the scale-dependent bias introduced by primordial\nnon-Gaussianity on large scales. We derive and employ a power spectrum\nestimator using optimal weights that account for the redshift evolution of the\nPNG signal. We find constraints of $-515$. HLS0918 has a total far-infrared (FIR) luminosity\nL_FIR(8-1000um) = (1.6$\\pm$0.1)x10^14 L_sun/mu, where the total magnification\nmu_total = 8.9$\\pm$1.9, via a new lens model from the [CII] and continuum maps.\nDespite a HyLIRG luminosity, the FIR continuum shape resembles that of a local\nLIRG. We simultaneously fit all of the observed spectral line profiles, finding\nfour components which correspond cleanly to discrete spatial structures\nidentified in the maps. The two most redshifted spectral components occupy the\nnucleus of a massive galaxy, with a source plane separation <1 kpc. The reddest\ndominates the continuum map (de-magnified L_FIR = (1.1$\\pm$0.2)x10^13 L_sun),\nand excites strong water emission in both nuclear components via a powerful FIR\nradiation field from the intense star formation. A third star-forming component\nis most likely a region of a merging companion (dV ~ 500 km/s) exhibiting\ngenerally similar gas properties. The bluest component originates from a\nspatially distinct region, and photo-dissociation region (PDR) analysis\nsuggests that it is lower density, cooler and forming stars less vigorously\nthan the other components. Strikingly, it has very strong [NII] emission which\nmay suggest an ionized, molecular outflow. This comprehensive view of gas\nproperties and morphology in HLS0918 previews the science possible for a large\nsample of high-redshift galaxies once ALMA attains full sensitivity.", "category": "astro-ph_CO" }, { "text": "Analyzing the 21-cm signal brightness temperature in the Universe with\n inhomogeneities: We explore the 21-cm signal in our Universe containing inhomogeneous matter\ndistribution at considerably large scales. Employing Buchert's averaging\nprocedure in the context of a model of spacetime with multiple inhomogeneous\ndomains, we evaluate the effect of our model parameters on the observable 21-cm\nsignal brightness temperature. Our model parameters are constrained through the\nMarkov Chain Monte Carlo method using the Union 2.1 supernova Ia observational\ndata. We find that a significant dip in the brightness temperature compared to\nthe $\\Lambda$CDM prediction could arise as an effect of the inhomogeneities\npresent in the Universe.", "category": "astro-ph_CO" }, { "text": "Radio Band Observations of Blazar Variability: The properties of blazar variability in the radio band are studied using the\nunique combination of temporal resolution from single dish monitoring and\nspatial resolution from VLBA imaging; such measurements, now available in all\nfour Stokes parameters, together with theoretical simulations, identify the\norigin of radio band variability and probe the characteristics of the radio jet\nwhere the broadband blazar emission originates. Outbursts in total flux density\nand linear polarization in the optical-to-radio bands are attributed to shocks\npropagating within the jet spine, in part based on limited modeling invoking\ntransverse shocks; new radiative transfer simulations allowing for shocks at\narbitrary angle to the flow direction confirm this picture by reproducing the\nobserved centimeter-band variations observed more generally, and are of current\ninterest since these shocks may play a role in the gamma-ray flaring detected\nby Fermi. Recent UMRAO multifrequency Stokes V studies of bright blazars\nidentify the spectral variability properties of circular polarization for the\nfirst time and demonstrate that polarity flips are relatively common.\nAll-Stokes data are consistent with the production of circular polarization by\nlinear-to-circular mode conversion in a region that is at least partially\nself-absorbed. Detailed analysis of single-epoch, multifrequency, all-Stokes\nVLBA observations of 3C 279 support this physical picture and are best\nexplained by emission from an electron-proton plasma.", "category": "astro-ph_CO" }, { "text": "The incidence of cool gas in ~ 1e13 Msun halos: We present the first results of an ongoing spectroscopic follow-up of close\nluminous red galaxy (LRGs) and MgII {\\lambda}{\\lambda} 2796,2803 absorber pairs\nfor an initial sample of 15 photometrically selected LRGs at physical projected\nseparations {\\rho} \\le 350 kpc/h from a QSO sightline. Our moderate-resolution\nspectra confirm a physical association between the cool gas (T ~ 1e4 K)\nrevealed by the presence of MgII absorption features and the LRG halo in five\ncases. In addition, we report an empirical estimate of the maximum covering\nfraction (\\kappa_max) of cool gas in massive, \\ge 1e13 Msun/h dark matter halos\nhosting LRGs at z ~ 0.5. This study is performed using a sample of foreground\nLRGs that are located at {\\rho} < 400 kpc/h from a QSO sightline. The LRGs are\nselected to have a robust photometric redshift \\sigma_z/(1+z_ph) \\approx 0.03.\nWe determine \\kappa_max based on the incidence of MgII absorption systems that\noccur within z_ph +/- 3sigma_z in the spectra of the background QSOs. Despite\nthe large uncertainties in z_ph, this experiment provides a conservative upper\nlimit to the covering fraction of cool gas in the halos of LRGs. We find that\n\\kappa_max \\approx 0.07 at W_r(2796) \\ge 1.0 A and \\kappa_max \\approx 0.18 at\nW_r(2796) \\ge 0.5 A, averaged over 400 kpc/h radius. Our study shows that while\ncool gas is present in \\ge 1e13 Msun/h halos, the mean covering fraction of\nstrong absorbers is no more than 7%.", "category": "astro-ph_CO" }, { "text": "Dynamical processes in galaxy centers: How does the gas get in nuclear regions to fuel black holes? How efficient is\nthe feedback? The different processes to cause rapid gas inflow (or outflow) in\ngalaxy centers are reviewed. Non axisymmetries can be created or maintained by\ninternal disk instabilities, or galaxy interactions. Simulations and\nobservations tell us that the fueling is a chaotic and intermittent process,\nwith different scenarios and time-scales, according to the various radial\nscales across a galaxy.", "category": "astro-ph_CO" }, { "text": "Inflation with an extra light scalar field after Planck: Bayesian inference techniques are used to investigate situations where an\nadditional light scalar field is present during inflation and reheating. This\nincludes (but is not limited to) curvaton-type models. We design a numerical\npipeline where $\\simeq 200$ inflaton setups $\\times\\, 10$ reheating scenarios\n$= 2000$ models are implemented and we present the results for a few\nprototypical potentials. We find that single-field models are remarkably robust\nunder the introduction of light scalar degrees of freedom. Models that are\nruled out at the single-field level are not improved in general, because good\nvalues of the spectral index and the tensor-to-scalar ratio can only be\nobtained for very fine-tuned values of the extra field parameters and/or when\nlarge non-Gaussianities are produced. The only exception is quartic large-field\ninflation, so that the best models after Planck are of two kinds: plateau\npotentials, regardless of whether an extra field is added or not, and quartic\nlarge-field inflation with an extra light scalar field, in some specific\nreheating scenarios. Using Bayesian complexity, we also find that more\nparameters are constrained for the models we study than for their single-field\nversions. This is because the added parameters not only contribute to the\nreheating kinematics but also to the cosmological perturbations themselves, to\nwhich the added field contributes. The interplay between these two effects lead\nto a suppression of degeneracies that is responsible for having more\nconstrained parameters.", "category": "astro-ph_CO" }, { "text": "Semi-blind Bayesian inference of CMB map and power spectrum: We present a new blind formulation of the Cosmic Microwave Background (CMB)\ninference problem. The approach relies on a phenomenological model of the\nmulti-frequency microwave sky without the need for physical models of the\nindividual components. For all-sky and high resolution data, it unifies parts\nof the analysis that have previously been treated separately, such as component\nseparation and power spectrum inference. We describe an efficient sampling\nscheme that fully explores the component separation uncertainties on the\ninferred CMB products such as maps and/or power spectra. External information\nabout individual components can be incorporated as a prior giving a flexible\nway to progressively and continuously introduce physical component separation\nfrom a maximally blind approach. We connect our Bayesian formalism to existing\napproaches such as Commander, SMICA and ILC, and discuss possible future\nextensions.", "category": "astro-ph_CO" }, { "text": "The Entrainment-Limited Evolution of FR II Sources: Maximum Sizes and A\n Possible Connection to FR Is: We construct a simple theoretical model to investigate how entrainment\ngradually erodes high-speed FR II jets. This process is described by embedding\na mixing-layer model developed originally to describe FR I objects in a\nself-similar model for the lobe structure of classical FR II sources. Following\nthe classical FR II models, we assume that the lobe is dominated by the\nparticles injected from the central jet. The entrainment produces a boundary\nshear layer which acts at the interface between the dense central jet and the\nless denser surrounding lobe, and the associated erosion of the jet places\ninteresting limits on the maximum size of FR II sources. The model shows that\nthis limit depends mainly on the initial bulk velocity of the relativistic jet\ntriggered. The bulk velocities of FR IIs suggested by our model are in good\nagreement with that obtained from direct pc-scale observations on ordinary\nradio galaxies and quasars. Finally, we discuss how FR IIs may evolve into FR\nIs upon reaching their maximum, entrainment-limited sizes.", "category": "astro-ph_CO" }, { "text": "The spectral index of polarized diffuse Galactic emission between 30 and\n 44 GHz: We present an estimate of the polarized spectral index between the Planck 30\nand 44 GHz surveys in $3.7^\\circ$ pixels across the entire sky. We use an\nobjective reference prior that maximises the impact of the data on the\nposterior and multiply this by a maximum entropy prior that includes\ninformation from observations in total intensity by assuming a polarization\nfraction. Our parametrization of the problem allows the reference prior to be\neasily determined and also provides a natural method of including prior\ninformation. The spectral index map is consistent with those found by others\nbetween surveys at similar frequencies. Across the entire sky we find an\naverage temperature spectral index of $-2.99\\pm0.03(\\pm1.12)$ where the first\nerror term is the statistical uncertainty on the mean and the second error term\n(in parentheses) is the extra intrinsic scatter in the data. We use a\nclustering algorithm to identify pixels with actual detections of the spectral\nindex. The average spectral index in these pixels is $-3.12\\pm0.03(\\pm0.64)$\nand then when also excluding pixels within $10^\\circ$ of the Galactic plane we\nfind $-2.92(\\pm0.03)$. We find a statistically significant difference between\nthe average spectral indices in the North and South Fermi bubbles. Only\nincluding pixels identified by the clustering algorithm, the average spectral\nindex in the southern bubble is $-3.00\\pm0.05(\\pm0.35)$, which is similar to\nthe average across the whole sky. In the northern bubble we find a much harder\naverage spectral index of $-2.36\\pm0.09(\\pm0.63)$. Therefore, if the bubbles\nare features in microwave polarization they are not symmetric about the\nGalactic plane.", "category": "astro-ph_CO" }, { "text": "Microwave Spectro-Polarimetry of Matter and Radiation across Space and\n Time: This paper discusses the science case for a sensitive spectro-polarimetric\nsurvey of the microwave sky. Such a survey would provide a tomographic and\ndynamic census of the three-dimensional distribution of hot gas, velocity\nflows, early metals, dust, and mass distribution in the entire Hubble volume,\nexploit CMB temperature and polarisation anisotropies down to fundamental\nlimits, and track energy injection and absorption into the radiation background\nacross cosmic times by measuring spectral distortions of the CMB blackbody\nemission. In addition to its exceptional capability for cosmology and\nfundamental physics, such a survey would provide an unprecedented view of\nmicrowave emissions at sub-arcminute to few-arcminute angular resolution in\nhundreds of frequency channels, a data set that would be of immense legacy\nvalue for many branches of astrophysics. We propose that this survey be\ncarried-out with a large space mission featuring a broad-band polarised imager\nand a moderate resolution spectro-imager at the focus of a 3.5m aperture\ntelescope actively cooled to about 8K, complemented with absolutely-calibrated\nFourier Transform Spectrometer modules observing at degree-scale angular\nresolution in the 10-2000 GHz frequency range. We propose two observing modes:\na survey mode to map the entire sky as well as a few selected wide fields, and\nan observatory mode for deeper observations of regions of specific interest.", "category": "astro-ph_CO" }, { "text": "Prospects for Detecting Dark Matter Halo Substructure with Pulsar Timing: One of the open questions of modern cosmology is the nature and properties of\nthe Dark Matter halo and its substructures. In this work we study the\ngravitational effect of dark matter substructures on pulsar timing\nobservations. Since millisecond pulsars are stable and accurate emitters, they\nhave been proposed as plausible astrophysical tools to probe the gravitational\neffects of dark matter structures. We study this effect on pulsar timing\nthrough Shapiro time delay (or Integrated Sachs-Wolfe (ISW) effect) and Doppler\neffects statistically, showing that the latter dominates the signal. For this\ntask, we relate the power spectrum of pulsar frequency change to the matter\npower spectrum on small scales, which we compute using the stable clustering\nhypothesis. We compare this power spectrum with the reach of current and future\nobservations of pulsar timing designed for gravitational wave (GW) detection.\nOur results show that while current observations are unable to detect these\nsignals, the sensitivity of the upcoming Square Kilometer Array (SKA) is only a\nfactor of few weaker than our optimistic predictions.", "category": "astro-ph_CO" }, { "text": "The GALEX Arecibo SDSS Survey V: The Relation between the HI Content of\n Galaxies and Metal Enrichment at their Outskirts: We have obtained long-slit spectra of 174 star-forming galaxies with stellar\nmasses greater than 10^10 M_\\odot from the GALEX Arecibo SDSS (GASS) survey.\nThese galaxies have both HI and H_2 mass measurements. The average metallicity\nprofile is strikingly flat out to R_90, the radius enclosing 90% of the r-band\nlight. Metallicity profiles which decline steadily with radius are found\nprimarily for galaxies in our sample with low stellar mass (Log(M_*)<10.2),\nconcentration, and/or mean stellar mass density. Beyond ~R_90, however, around\n10 percent of the galaxies in our sample exhibit a sharp downturn in\nmetallicity. Remarkably, we find that the magnitude of the outer metallicity\ndrop is well correlated with the total HI content of the galaxy (measured as\nf_HI=M_HI/M_*). We examine the radial profiles of stellar population ages and\nstar formation rate densities, and conclude that the galaxies with largest\nouter metallicity drops are actively growing their stellar disks, with mass\ndoubling times across the whole disk only one third as long as a typical GASS\ngalaxy. We also describe a correlation between local stellar mass density and\nmetallicity, which is valid across all galaxies in our sample. We argue that\nmuch of the recent stellar mass growth at the edges of these galaxies can be\nlinked to the accretion or radial transport of relatively pristine gas from\nbeyond the galaxies' stellar disks.", "category": "astro-ph_CO" }, { "text": "VIPERS: An Unprecedented View of Galaxies and Large-Scale Structure\n Halfway Back in the Life of the Universe: The VIMOS Public Extragalactic Redshift Survey (VIPERS) is an ongoing ESO\nLarge Programme to map in detail the large-scale distribution of galaxies at\n0.5 < z <1.2. With a combination of volume and sampling density that is unique\nfor these redshifts, it focuses on measuring galaxy clustering and related\ncosmological quantities as part of the grand challenge of understanding the\norigin of cosmic acceleration. VIPERS has also been designed to guarantee a\nbroader legacy, allowing detailed investigations of the properties and\nevolutionary trends of z~1 galaxies. The survey strategy exploits the specific\nadvantages of the VIMOS spectrograph at the VLT, aiming at a final sample of\nnearly 100,000 galaxy redshifts to iAB = 22.5 mag, which represents the largest\nredshift survey ever performed with ESO telescopes. In this introductory\narticle we describe the survey construction, together with early results based\non a first sample of ~55,000 galaxies.", "category": "astro-ph_CO" }, { "text": "Dust-to-metal ratios in damped Lyman-alpha absorbers: Fresh clues to the\n origins of dust and optical extinction towards gamma-ray bursts: Motivated by the anomalous dust-to-metal ratios derived in the literature for\ngamma-ray burst (GRB) damped Lyman-alpha absorbers (DLAs), we measure these\nratios using the dust-depletion pattern observed in UV/optical afterglow\nspectra associated with the ISM at the GRB host-galaxy redshifts. Our sample\nconsists of 20 GRB absorbers and a comparison sample of 72 QSO-DLAs with\nredshift 1.2 < z < 4.0 and down to Z = 0.002 Z_Sol metallicities. The\ndust-to-metal ratio in QSO- and GRB-DLAs increases both with metallicity and\nmetal column density, spanning ~10--110% of the Galactic value and pointing to\na non universal dust-to-metal ratio. The low values of dust-to-metal ratio\nsuggest that low-metallicity systems have lower dust fractions than typical\nspiral galaxies and perhaps that the dust in these systems is produced\ninefficiently, i.e. by grain growth in the low-metallicity regime with\nnegligible contribution from supernovae (SNe) and asymptotic giant branch (AGB)\nstars. On the other hand, some GRB- and QSO-DLAs show high dust-to-metal ratio\nvalues out to z ~ 4, requiring rapid dust production, such as in SN ejecta, but\nalso in AGB winds and via grain growth for the highest metallicity systems.\nGRB-DLAs overall follow the dust-to-metal-ratio properties of QSO-DLAs, GRBs\nprobing up to larger column and volume densities. For comparison, the\ndust-to-metal ratio that we derive for the SMC and LMC are ~82--100% and ~98%\nof the Galactic value, respectively. The literature dust-to-metal ratio of the\nlow-metallicity galaxy I Zw 18 (< 37%) is consistent with the distribution that\nwe find. The dust extinction Av increases steeply with the column density of\niron in dust, N(Fe)dust, calculated from relative metal abundances, confirming\nthat dust extinction is mostly occurring in the host galaxy ISM. Most GRB-DLAs\ndisplay log N(Fe)dust > 14.7, above which several QSO-DLAs reveal H2\n(abridged).", "category": "astro-ph_CO" }, { "text": "Clusters, Groups, and Filaments in the Chandra Deep Field-South up to\n Redshift 1: We present a comprehensive structure detection analysis of the 0.3 square\ndegree area of the MUSYC-ACES field which covers the Chandra Deep Field-South\n(CDFS). Using a density-based clustering algorithm on the MUSYC and ACES\nphotometric and spectroscopic catalogues we find 62 over-dense regions up to\nredshifts of 1, including, clusters, groups and filaments. All structures are\nconfirmed using the DBSCAN method, including the detection of nine structures\npreviously reported in the literature. We present a catalogue of all structures\npresent including their central position, mean redshift, velocity dispersions,\nand classification based on their morphological and spectroscopic\ndistributions. In particular we find 13 galaxy clusters and 6 large\ngroups/small clusters. Comparison of these massive structures with published\nXMM-Newton imaging (where available) shows that $80\\%$ of these structures are\nassociated with diffuse, soft-band (0.4 - 1 keV) X-ray emission including\n$90\\%$ of all objects classified as clusters. The presence of soft-band X-ray\nemission in these massive structures (${\\rm M}_{200} \\geq 4.9 \\times 10^{13}\n{\\rm M}_{\\odot}$) provides a strong independent confirmation of our methodology\nand classification scheme. Nearly $60\\%$ of the clusters, groups and filaments\nare detected in the known enhanced density regions of the CDFS at\n$z\\simeq0.13$, $z\\simeq0.52$, $0.68$, and $0.73$. Additionally, all of the\nclusters, bar the most distant, are found in these over-dense redshifts\nregions. Many of the clusters and groups exhibit signs of on-going formation\nseen in their velocity distributions, position within the detected cosmic web\nand in one case through the presence of tidally disrupted central galaxies\nexhibiting trails of stars. These results all provide strong support for\nhierarchical structure formation up to redshifts of 1.", "category": "astro-ph_CO" }, { "text": "Symbolic Implementation of Extensions of the $\\texttt{PyCosmo}$\n Boltzmann Solver: $\\texttt{PyCosmo}$ is a Python-based framework for the fast computation of\ncosmological model predictions. One of its core features is the symbolic\nrepresentation of the Einstein-Boltzmann system of equations. Efficient\n$\\texttt{C/C++}$ code is generated from the $\\texttt{SymPy}$ symbolic\nexpressions making use of the $\\texttt{sympy2c}$ package. This enables easy\nextensions of the equation system for the implementation of new cosmological\nmodels. We illustrate this with three extensions of the $\\texttt{PyCosmo}$\nBoltzmann solver to include a dark energy component with a constant equation of\nstate, massive neutrinos and a radiation streaming approximation. We describe\nthe $\\texttt{PyCosmo}$ framework, highlighting new features, and the symbolic\nimplementation of the new models. We compare the $\\texttt{PyCosmo}$ predictions\nfor the $\\Lambda$CDM model extensions with $\\texttt{CLASS}$, both in terms of\naccuracy and computational speed. We find a good agreement, to better than 0.1%\nwhen using high-precision settings and a comparable computational speed. Links\nto the Python Package Index (PyPI) page of the code release and to the PyCosmo\nHub, an online platform where the package is installed, are available at:\nhttps://cosmology.ethz.ch/research/software-lab/PyCosmo.html.", "category": "astro-ph_CO" }, { "text": "Reconstructing Redshift Distributions with Cross-Correlations: Tests and\n an Optimized Recipe: Many of the cosmological tests to be performed by planned dark energy\nexperiments will require extremely well-characterized photometric redshift\nmeasurements. Current estimates are that the true mean redshift of the objects\nin each photo-z bin must be known to better than 0.002(1+z) if errors in\ncosmological measurements are not to be degraded. A conventional approach is to\ncalibrate these photometric redshifts with large sets of spectroscopic\nredshifts. However, at the depths probed by Stage III surveys (such as DES),\nlet alone Stage IV (LSST, JDEM, Euclid), existing large redshift samples have\nall been highly (25-60%) incomplete. A powerful alternative approach is to\nexploit the clustering of galaxies to perform photometric redshift\ncalibrations. Measuring the two-point angular cross-correlation between objects\nin some photometric redshift bin and objects with known spectroscopic redshift\nallows the true redshift distribution of a photometric sample to be\nreconstructed in detail, even if it includes objects too faint for spectroscopy\nor if spectroscopic samples are highly incomplete. We test this technique using\nmock DEEP2 Galaxy Redshift survey light cones constructed from the Millennium\nSimulation semi-analytic galaxy catalogs. From this realistic test, we find\nthat the true redshift distribution of a photometric sample can, in fact, be\ndetermined accurately with cross-correlation techniques. We also compare the\nempirical error in the reconstruction of redshift distributions to previous\nanalytic predictions, finding that additional components must be included in\nerror budgets to match the simulation results. We conclude by presenting a\nstep-by-step, optimized recipe for reconstructing redshift distributions using\nstandard correlation measurements.", "category": "astro-ph_CO" }, { "text": "On approximations of the redshift-space bispectrum and power spectrum\n multipoles covariance matrix: We investigate, in dark matter and galaxy mocks, the effects of approximating\nthe galaxy power spectrum-bispectrum estimated covariance as a diagonal matrix,\nfor an analysis that aligns with the specifications of recent and upcoming\ngalaxy surveys. We find that, for a joint power spectrum and bispectrum\ndata-vector, with corresponding $k$-ranges of $0.0225$ ($20 - 30 \\%$ for\n$k_{\\parallel} \\gtrsim 0.02 \\,h^{-1}$Mpc), in the presence of polarization\nleakage. Our results are robust also when up to $40\\%$ of channels are missing,\nmimicking a Radio Frequency Interference (RFI) flagging of the data. Having\nquantified the notable effect of polarisation leakage on our results, in\nperspective we advocate the use of more realistic simulations when testing 21\ncm intensity mapping capabilities.", "category": "astro-ph_CO" }, { "text": "Orthogonal BipoSH measures : Scrutinizing sources of isotropy violation: The two point correlation function of the CMB temperature anisotropies is\ngenerally assumed to be statistically isotropic (SI). Deviations from this\nassumption could be traced to physical or observational artefacts and\nsystematic effects. Measurement of non-vanishing power in the BipoSH spectra is\na standard statistical technique to search for isotropy violations. Although\nthis is a neat tool allowing a blind search for SI violations in the CMB sky,\nit is not easy to discern the cause of isotropy violation using this measure.\nIn this article, we propose a novel technique of constructing orthogonal BipoSH\nestimators, which can be used to discern between models of isotropy violation.", "category": "astro-ph_CO" }, { "text": "Dark energy and dark matter perturbations in singular universes: We discuss the evolution of density perturbations of dark matter and dark\nenergy in cosmological models which admit future singularities in a finite\ntime. Up to now geometrical tests of the evolution of the universe do not\ndifferentiate between singular universes and $\\Lambda$CDM scenario. We solve\nperturbation equations using the gauge invariant formalism. The analysis shows\nthat the detailed reconstruction of the evolution of perturbations within\nsingular cosmologies, in the dark sector, exhibit important differences between\nthe singular universes models and the $\\Lambda$CDM cosmology. This is\nencouraging for further examination and gives hope for discriminating between\nthose models with future galaxy weak lensing experiments like the Dark Energy\nSurvey (DES) and Euclid or CMB observations like PRISM and CoRE.", "category": "astro-ph_CO" }, { "text": "Turbulent formation of protogalaxies at the plasma to gas transition: The standard model of gravitational structure formation is based on the Jeans\n1902 acoustic theory, neglecting crucial effects of viscosity, turbulence and\ndiffusion. A Jeans length scale L_J emerges that exceeds the scale of causal\nconnection ct during the plasma epoch. Photon-viscous forces initially dominate\nall others including gravity. The first structures formed were at density\nminima by fragmentation when the viscous-gravitional scale L_SV matched ct at\n30,000 years to produce protosupercluster voids and protosuperclusters. Weak\nturbulence produced at expanding void boundaries guides the morphology of\nsmaller fragments down to protogalaxy size just before transition to gas at\n300,000 years. The observed 10^20 meter size of protogalaxies reflects the\nplasma Kolmogorov scale with Nomura linear and spiral morphology. On transition\nto gas the kinematic viscosity decreases so the protogalaxies fragment into\nJeans scale clouds, each with a trillion earth-mass planets. The planets form\nstars near the cores of the protogalaxies. High resolution images of planetary\nnebula and supernova remnants reveal thousands of frozen hydrogen-helium dark\nmatter planets. Galaxy mergers show frictional trails of young globular\nclusters formed in place, proving that dark matter halos of galaxies consist of\ndark matter planets in metastable clumps.", "category": "astro-ph_CO" }, { "text": "Redshifted 21-cm bispectrum II: Impact of the spin temperature\n fluctuations and redshift space distortions on the signal from the Cosmic\n Dawn: We present a study of the 21-cm signal bispectrum (which quantifies the\nnon-Gaussianity in the signal) from the Cosmic Dawn (CD). For our analysis, we\nhave simulated the 21-cm signal using radiative transfer code GRIZZLY, while\nconsidering two types of sources (mini-QSOs and HMXBs) for Ly$\\alpha$ coupling\nand the X-ray heating of the IGM. Using this simulated signal, we have, for the\nfirst time, estimated the CD 21-cm bispectra for all unique $k$-triangles and\nfor a range of $k$ modes. We observe that the redshift evolution of the\nbispectra magnitude and sign follow a generic trend for both source models.\nHowever, the redshifts at which the bispectra magnitude reach their maximum and\nminimum values and show their sign reversal depends on the source model. When\nthe Ly$\\alpha$ coupling and the X-ray heating of the IGM occur simultaneously,\nwe observe two consecutive sign reversals in the bispectra for small\n$k$-triangles (irrespective of the source models). One arising at the beginning\nof the IGM heating and the other at the end of Ly$\\alpha$ coupling saturation.\nThis feature can be used in principle to constrain the CD history and/or to\nidentify the specific CD scenarios. We also quantify the impact of the spin\ntemperature ($T_{\\rm S}$) fluctuations on the bispectra. We find that $T_{\\rm\nS}$ fluctuations have maximum impact on the bispectra magnitude for small\n$k$-triangles and at the stage when Ly$\\alpha$ coupling reaches saturation.\nFurthermore, we are also the first to quantify the impact of redshift space\ndistortions (RSD), on the CD bispectra. We find that the impact of RSD on the\nCD 21-cm bispectra is significant ($> 20\\%$) and the level depends on the\nstages of the CD and the $k$-triangles for which the bispectra are being\nestimated.", "category": "astro-ph_CO" }, { "text": "Magnetic fields from cosmological bulk flows: We explore the possibility that matter bulk flows could generate the required\nvorticity in the electron-proton-photon plasma to source cosmic magnetic fields\nthrough the Harrison mechanism. We analyze the coupled set of perturbed Maxwell\nand Boltzmann equations for a plasma in which the matter and radiation\ncomponents exhibit relative bulk motions at the background level. We find that,\nto first order in cosmological perturbations, bulk flows with velocities\ncompatible with current Planck limits ($\\beta<8.5\\times 10^{-4}$ at $95\\%$ CL)\ncould generate magnetic fields with an amplitude $10^{-21}$ G on 10 kpc\ncomoving scales at the time of completed galaxy formation which could be\nsufficient to seed a galactic dynamo mechanism.", "category": "astro-ph_CO" }, { "text": "Signatures of Modified Gravity on the 21-cm Power Spectrum at\n Reionisation: Scalar modifications of gravity have an impact on the growth of structure.\nBaryon and Cold Dark Matter (CDM) perturbations grow anomalously for scales\nwithin the Compton wavelength of the scalar field. In the late time Universe\nwhen reionisation occurs, the spectrum of the 21cm brightness temperature is\nthus affected. We study this effect for chameleon-f(R) models, dilatons and\nsymmetrons. Although the f(R) models are more tightly constrained by solar\nsystem bounds, and effects on dilaton models are negligible, we find that\nsymmetrons where the phase transition occurs before z_* ~ 12 will be detectable\nfor a scalar field range as low as 5 kpc. For all these models, the detection\nprospects of modified gravity effects are higher when considering modes\nparallel to the line of sight where very small scales can be probed. The study\nof the 21 cm spectrum thus offers a complementary approach to testing modified\ngravity with large scale structure surveys. Short scales, which would be highly\nnon-linear in the very late time Universe when structure forms and where\nmodified gravity effects are screened, appear in the linear spectrum of 21 cm\nphysics, hence deviating from General Relativity in a maximal way.", "category": "astro-ph_CO" }, { "text": "$\u03b3$ gravity: Steepness control: We investigate a simple generalization of the metric exponential $f(R)$\ngravity theory that is cosmologically viable and compatible with solar system\ntests of gravity. We show that, as compared to other viable $f(R)$ theories,\nits steep dependence on the Ricci scalar $R$ facilitates agreement with\nstructure constraints, opening the possibility of $f(R)$ models with\nequation-of-state parameter that could be differentiated from a cosmological\nconstant ($w_{de}=-1$) with future surveys at both background and perturbative\nlevels.", "category": "astro-ph_CO" }, { "text": "Turnaround radius in $\u039b$CDM, and dark matter cosmologies II: the\n role of dynamical friction: This paper is an extension of the paper by Del Popolo, Chan, and Mota (2020)\nto take account the effect of dynamical friction. We show how dynamical\nfriction changes the threshold of collapse, $\\delta_c$, and the turn-around\nradius, $R_t$. We find numerically the relationship between the turnaround\nradius, $R_{\\rm t}$, and mass, $M_{\\rm t}$, in $\\Lambda$CDM, in dark energy\nscenarios, and in a $f(R)$ modified gravity model. Dynamical friction gives\nrise to a $R_{\\rm t}-M_{\\rm t}$ relation differing from that of the standard\nspherical collapse. In particular, dynamical friction amplifies the effect of\nshear, and vorticity already studied in Del Popolo, Chan, and Mota (2020). A\ncomparison of the $R_{\\rm t}-M_{\\rm t}$ relationship for the $\\Lambda$CDM, and\nthose for the dark energy, and modified gravity models shows, that the $R_{\\rm\nt}-M_{\\rm t}$ relationship of the $\\Lambda$CDM is similar to that of the dark\nenergy models, and small differences are seen when comparing with the $f(R)$\nmodels. The effect of shear, rotation, and dynamical friction is particularly\nevident at galactic scales, giving rise to a difference between the $R_{\\rm\nt}-M_{\\rm t}$ relation of the standard spherical collapse of the order of\n$\\simeq 60\\%$. Finally, we show how the new values of the $R_{\\rm t}-M_{\\rm t}$\ninfluence the constraints to the $w$ parameter of the equation of state.", "category": "astro-ph_CO" }, { "text": "Filament Hunting: Integrated HI 21cm Emission From Filaments Inferred by\n Galaxy Surveys: Large scale filaments, with lengths that can reach tens of Mpc, are the most\nprominent features in the cosmic web. These filaments have only been observed\nindirectly through the positions of galaxies in large galaxy surveys or through\nabsorption features in the spectra of high redshift sources. In this study we\npropose to go one step further and directly detect intergalactic medium\nfilaments through their emission in the HI 21cm line. We make use of high\nresolution cosmological simulations to estimate the intensity of this emission\nin low redshift filaments and use it to make predictions for the direct\ndetectability of specific filaments previously inferred from galaxy surveys, in\nparticular the Sloan Digital Sky Survey. Given the expected signal of these\nfilaments our study shows that HI emission from large filaments can be observed\nby current and next generation radio telescopes. We estimate that gas in\nfilaments of length $l \\gtrsim$ 15 $h^{-1}$Mpc with relatively small\ninclinations to the line of sight ($\\lesssim 10^\\circ$) can be observed in\n$\\sim40-100$ hours with telescopes such as GMRT or EVLA, potentially providing\nlarge improvements over our knowledge of the astrophysical properties of these\nfilaments. Due to their large field of view and sufficiently long integration\ntimes, upcoming HI surveys with the Apertif and ASKAP instruments will be able\nto detect large filaments independently of their orientation and curvature.\nFurthermore, our estimates indicate that a more powerful future radio telescope\nlike SKA-2 can be used to map most of these filaments, which will allow them to\nbe used as a strong cosmological probe.", "category": "astro-ph_CO" }, { "text": "RXJ 0921+4529: a binary quasar or gravitational lens?: We report the new spectroscopic observations of the gravitational lens RXJ\n021+4529 with the multi-mode focal reducer SCORPIO of the SAO RAS 6-m\ntelescope. The new spectral observations were compared with the previously\nobserved spectra of components A and B of RXJ 0921+4529, i.e. the same\ncomponents observed in different epochs. We found a significant difference in\nthe spectrum between the components that cannot be explained with microlensing\nand/or spectral variation. We conclude that RXJ 0921+4529 is a binary quasar\nsystem, where redshifts of quasars A and B are 1.6535 +/- 0.0005 and 1.6625 +/-\n0.0015, respectively.", "category": "astro-ph_CO" }, { "text": "The contribution of star-forming galaxies to the cosmic radio background: Recent measurements of the temperature of the sky in the radio band, combined\nwith literature data, have convincingly shown the existence of a cosmic radio\nbackground with an amplitude of $\\sim 1$ K at 1 GHz and a spectral energy\ndistribution that is well described by a power law with index $\\alpha \\simeq\n-0.6$. The origin of this signal remains elusive, and it has been speculated\nthat it could be dominated by the contribution of star-forming galaxies at high\nredshift \\change{if the far infrared-radio correlation $q(z)$ evolved} in time.\n\\change{We fit observational data from several different experiments by the\nrelation $q(z) \\simeq q_0 - \\beta \\log(1+z)$ with $q_0 = 2.783 \\pm 0.024$ and\n$\\beta = 0.705 \\pm 0.081$ and estimate the total radio emission of the whole\ngalaxy population at any given redshift from the cosmic star formation rate\ndensity at that redshift. It is found that} star-forming galaxies can only\naccount for $\\sim$13 percent of the observed intensity of the cosmic radio\nbackground.", "category": "astro-ph_CO" }, { "text": "Millennium Simulation Dark Matter Haloes: Multi-fractal and Lacunarity\n Analysis with Homogeneity Transition: We investigate from the fractal viewpoint the way in which the dark matter is\ngrouped at z = 0 in the Millennium dark matter cosmological simulation. The\ndetermination of the cross to homogeneity in the Millennium Simulation data is\ndescribed from the behaviour of the fractal dimension and the lacunarity. We\nuse the sliding window technique to calculate the fractal mass-radius\ndimension, the pre-factor F and the lacunarity of this fractal relation.\nBesides, we determinate the multi-fractal dimension and the lacunarity\nspectrum, including their dependence with radial distance. This calculations\nshow a radial distance dependency of all the fractal quantities, with\nheterogeneity clustering of dark matter haloes up to depths of 100 Mpc/h. The\ndark matter haloes clustering in the Millennium Simulation shows a radial\ndistance dependency, with two regions clearly defined. The lacunarity spectrum\nfor values of the structure parameter q >= 1 shows regions with relative\nmaxima, revealing the formation of clusters and voids in the dark matter haloes\ndistribution. With the use of the multi-fractal dimension and the lacunarity\nspectrum, the transition to homogeneity at depths between 100 Mpc/h and 120\nMpc/h for the Millennium Simulation dark matter haloes is detected.", "category": "astro-ph_CO" }, { "text": "The effects of peculiar velocities on the morphological properties of\n large-scale structure: It is known that the large-scale structure (LSS) mapped by a galaxy redshift\nsurvey is subject to distortions by galaxies' peculiar velocities. Besides the\nsignatures generated in common N-point statistics, such as the anisotropy in\nthe galaxy 2-point correlation function, the peculiar velocities also induce\ndistinct features in LSS's morphological properties, which are fully described\nby four Minkowski functionals (MFs), i.e., the volume, surface area, integrated\nmean curvature and Euler characteristic (or genus). In this work, by using\nlarge suite of N-body simulations, we present and analyze these important\nfeatures in the MFs of LSS on both (quasi-)linear and non-linear scales, with a\nfocus on the latter. We also find the MFs can give competitive constraints on\ncosmological parameters compared to the power spectrum, probablly due to the\nnon-linear information contained. For galaxy number density similar to the DESI\nBGS galaxies, the constraint on $\\sigma_8$ from the MFs with one smoothing\nscale can be better by $\\sim 50\\%$ than from the power spectrum. These findings\nare important for the cosmological applications of MFs of LSS, and probablly\nopen up a new avenue for studying the peculiar velocity field itself.", "category": "astro-ph_CO" }, { "text": "MC^2: A deeper look at ZwCl 2341.1+0000 with Bayesian galaxy clustering\n and weak lensing analyses: ZwCl 2341.1+0000, a merging galaxy cluster with disturbed X-ray morphology\nand widely separated ($\\sim$3 Mpc) double radio relics, was thought to be an\nextremely massive ($10-30 \\times 10^{14} M_\\odot$) and complex system with\nlittle known about its merger history. We present JVLA 2-4 GHz observations of\nthe cluster, along with new spectroscopy from our Keck/DEIMOS survey, and apply\nGaussian Mixture Modeling to the three-dimensional distribution of 227\nconfirmed cluster galaxies. After adopting the Bayesian Information Criterion\nto avoid overfitting, which we discover can bias total dynamical mass estimates\nhigh, we find that a three-substructure model with a total dynamical mass\nestimate of $9.39 \\pm 0.81 \\times 10^{14} M_\\odot$ is favored. We also present\ndeep Subaru imaging and perform the first weak lensing analysis on this system,\nobtaining a weak lensing mass estimate of $5.57 \\pm 2.47 \\times 10^{14}\nM_\\odot$. This is a more robust estimate because it does not depend on the\ndynamical state of the system, which is disturbed due to the merger. Our\nresults indicate that ZwCl 2341.1+0000 is a multiple merger system comprised of\nat least three substructures, with the main merger that produced the radio\nrelics occurring near to the plane of the sky, and a younger merger in the\nNorth occurring closer to the line of sight. Dynamical modeling of the main\nmerger reproduces observed quantities (relic positions and polarizations,\nsubcluster separation and radial velocity difference), if the merger axis angle\nof $\\sim$10$^{+34}_{-6}$ degrees and the collision speed at pericenter is\n$\\sim$1900$^{+300}_{-200}$ km/s.", "category": "astro-ph_CO" }, { "text": "Extrasolar planets as a probe of modified gravity: We propose a new method to test modified gravity theories, taking advantage\nof the available data on extrasolar planets. We computed the deviations from\nthe Kepler third law and use that to constrain gravity theories beyond General\nRelativity. We investigate gravity models which incorporate three screening\nmechanisms: the Chameleon, the Symmetron and the Vainshtein. We find that data\nfrom exoplanets orbits are very sensitive to the screening mechanisms putting\nstrong constraints in the parameter space for the Chameleon models and the\nSymmetron, complementary and competitive to other methods, like interferometers\nand solar system. With the constraints on Vainshtein we are able to work beyond\nthe hypothesis that the crossover scale is of the same order of magnitude than\nthe Hubble radius $r_c \\sim H_0^{-1}$, which makes the screening work\nautomatically, testing how strong this hypothesis is and the viability of other\nscales.", "category": "astro-ph_CO" }, { "text": "Bayesian angular power spectrum analysis of interferometric data: We present a Bayesian angular power spectrum and signal map inference engine\nwhich can be adapted to interferometric observations of anisotropies inthe\ncosmic microwave background, 21 cm emission line mapping of galactic brightness\nfluctuations, or 21 cm absorption line mapping of neutral hydrogen in the dark\nages. The method uses Gibbs sampling to generate a sampled representation of\nthe angular power spectrum posterior and the posterior of signal maps given a\nset of measured visibilities in the uv-plane. We use a mock interferometric CMB\nobservation to demonstrate the validity of this method in the flat-sky\napproximation when adapted to take into account arbitrary coverage of the\nuv-plane, mode-mode correlations due to observations on a finite patch, and\nheteroschedastic visibility errors. The computational requirements scale as\nO(n_p log n_p) where n_p measures the ratio of the size of the detector array\nto the inter-detector spacing, meaning that Gibbs sampling is a promising\ntechnique for meeting the data analysis requirements of future cosmology\nmissions.", "category": "astro-ph_CO" }, { "text": "Features in single field slow-roll inflation: We compare the effects of local features (LF) and branch features (BF) of the\ninflaton potential on the spectrum of primordial perturbations. We show that LF\naffect the spectrum in a narrow range of scales while BF produce a step between\nlarge and small scales with respect to the featureless spectrum. We comment on\nthe possibility of distinguishing between these two types of feature models\nfrom the analysis of the Cosmic Microwave Background (CMB) radiation data.\n We also show that there exists a quantitative similarity between the\nprimordial spectra predicted by two of the BF potentials considered. This could\nlead to a degeneracy of their predicted CMB temperature spectra which could\nmake difficult to discriminate between the models from a CMB analysis. We\ncomment on the possibility that the degeneracy can be broken when higher order\nterms in the perturbations are considered. In this sense non-Gaussianity may\nplay an important role in discerning between different inflationary models\nwhich predict similar spectra.", "category": "astro-ph_CO" }, { "text": "Primordial feature constraints from BOSS+eBOSS: Understanding the universe in its pristine epoch is crucial in order to\nobtain a concise comprehension of the late-time universe. Although current data\nin cosmology are compatible with Gaussian primordial perturbations whose power\nspectrum follows a nearly scale-invariant power law, this need not be the case\nwhen a fundamental theoretical construction is assumed. These extended models\nlead to sharp features in the primordial power spectrum, breaking its scale\ninvariance. In this work, we obtain combined constraints on four primordial\nfeature models by using the final data release of the BOSS galaxies and eBOSS\nquasars. By pushing towards the fundamental mode of these surveys and using the\nlarger eBOSS volume, we were able to extend the feature parameter space (i.e.\nthe feature frequency $\\omega$) by a factor of four compared to previous\nanalyses using BOSS. While we did not detect any significant features, previous\nwork showed that next-generation galaxy surveys such as DESI will improve the\nsensitivity to features by a factor of 7, and will also extend the parameter\nspace by a factor of 2.5.", "category": "astro-ph_CO" }, { "text": "Morphological quenching of star formation: making early-type galaxies\n red: We point out a natural mechanism for quenching of star formation in\nearly-type galaxies. It automatically links the color of a galaxy with its\nmorphology and does not require gas consumption, removal or termination of gas\nsupply. Given that star formation takes place in gravitationally unstable gas\ndisks, it can be quenched when a disk becomes stable against fragmentation to\nbound clumps. This can result from the growth of a stellar spheroid, for\ninstance by mergers. We present the concept of morphological quenching (MQ)\nusing standard disk instability analysis, and demonstrate its natural\noccurrence in a cosmological simulation using an efficient zoom-in technique.\nWe show that the transition from a stellar disk to a spheroid can be sufficient\nto stabilize the gas disk, quench star formation, and turn an early-type galaxy\nred and dead while gas accretion continues. The turbulence necessary for disk\nstability can be stirred up by sheared perturbations within the disk in the\nabsence of bound star-forming clumps. While gas stripping processes are limited\nto dense groups and clusters, and other quenching mechanisms like AGN feedback,\nvirial shock heating and gravitational heating, are limited to halos more\nmassive than 10^12 Mo, the MQ can explain the appearance of red ellipticals\neven in less massive halos and in the field. The dense gas disks observed in\nsome of today's red ellipticals may be the relics of this mechanism, whereas\nred galaxies with quenched gas disks are expected to be more frequent at high\nredshift.", "category": "astro-ph_CO" }, { "text": "Probing high-redshift galaxies with Ly$\u03b1$ intensity mapping: We present a study of the cosmological Ly$\\alpha$ emission signal at $z > 4$.\nOur goal is to predict the power spectrum of the spatial fluctuations that\ncould be observed by an intensity mapping survey. The model uses the latest\ndata from the HST legacy fields and the abundance matching technique to\nassociate UV emission and dust properties with the halos, computing the\nemission from the interstellar medium (ISM) of galaxies and the intergalactic\nmedium (IGM), including the effects of reionization, self-consistently. The\nLy$\\alpha$ intensity from the diffuse IGM emission is 1.3 (2.0) times more\nintense than the ISM emission at $z = 4(7)$; both components are fair tracers\nof the star-forming galaxy distribution. However the power spectrum is\ndominated by ISM emission on small scales ($k > 0.01 h{\\rm Mpc}^{-1}$) with\nshot noise being significant only above $k = 1 h{\\rm Mpc}^{-1}$. At very lange\nscales ($k < 0.01h{\\rm Mpc}^{-1}$) diffuse IGM emission becomes important. The\ncomoving Ly$\\alpha$ luminosity density from IGM and galaxies, $\\dot \\rho_{{\\rm\nLy}\\alpha}^{\\rm IGM} = 8.73(6.51) \\times 10^{40} {\\rm erg}{\\rm s}^{-1}{\\rm\nMpc}^{-3}$ and $\\dot \\rho_{{\\rm Ly}\\alpha}^{\\rm ISM} = 6.62(3.21) \\times\n10^{40} {\\rm erg}{\\rm s}^{-1}{\\rm Mpc}^{-3}$ at $z = 4(7)$, is consistent with\nrecent SDSS determinations. We predict a power $k^3 P^{{\\rm Ly}\\alpha}(k,\nz)/2\\pi^2 = 9.76\\times 10^{-4}(2.09\\times 10^{-5}){\\rm nW}^2{\\rm m}^{-4}{\\rm\nsr}^{-2}$ at $z = 4(7)$ for $k = 0.1 h {\\rm Mpc}^{-1}$.", "category": "astro-ph_CO" }, { "text": "The connection between gamma-ray emission and millimeter flares in\n Fermi/LAT blazars: We compare the gamma-ray photon flux variability of northern blazars in the\nFermi/LAT First Source Catalog with 37 GHz radio flux density curves from the\nMetsahovi quasar monitoring program. We find that the relationship between\nsimultaneous millimeter (mm) flux density and gamma-ray photon flux is\ndifferent for different types of blazars. The flux relation between the two\nbands is positively correlated for quasars and does not exist for BLLacs.\nFurthermore, we find that the levels of gamma-ray emission in high states\ndepend on the phase of the high frequency radio flare, with the brightest\ngamma-ray events coinciding with the initial stages of a mm flare. The mean\nobserved delay from the beginning of a mm flare to the peak of the gamma-ray\nemission is about 70 days, which places the average location of the gamma-ray\nproduction at or downstream of the radio core. We discuss alternative scenarios\nfor the production of gamma-rays at distances of parsecs along the length the\njet.", "category": "astro-ph_CO" }, { "text": "On the Primordial Black Hole Mass Function for Broad Spectra: We elaborate on the mass function of primordial black holes in the case in\nwhich the power spectrum of the curvature perturbation is broad. For the case\nof a broad and flat spectrum, we argue that such a mass function is peaked at\nthe smallest primordial black mass which can be formed and possesses a tail\ndecaying like $M^{-3/2}$, where $M$ is the mass of the primordial black hole.", "category": "astro-ph_CO" }, { "text": "Nonsingular bouncing cosmologies in light of BICEP2: We confront various nonsingular bouncing cosmologies with the recently\nreleased BICEP2 data and investigate the observational constraints on their\nparameter space. In particular, within the context of the effective field\napproach, we analyze the constraints on the matter bounce curvaton scenario\nwith a light scalar field, and the new matter bounce cosmology model in which\nthe universe successively experiences a period of matter contraction and an\nekpyrotic phase. Additionally, we consider three nonsingular bouncing\ncosmologies obtained in the framework of modified gravity theories, namely the\nHo\\v{r}ava-Lifshitz bounce model, the $f(T)$ bounce model, and loop quantum\ncosmology.", "category": "astro-ph_CO" }, { "text": "The radial and azimuthal profiles of Mg II absorption around 0.5 < z <\n 0.9 zCOSMOS galaxies of different colors, masses and environments: We map the radial and azimuthal distribution of Mg II gas within 200 kpc\n(physical) of 4000 galaxies at redshifts 0.5 < z < 0.9 using co-added spectra\nof more than 5000 background galaxies at z > 1. We investigate the variation of\nMg II rest frame equivalent width as a function of the radial impact parameter\nfor different subsets of foreground galaxies selected in terms of their\nrest-frame colors and masses. Blue galaxies have a significantly higher average\nMg II equivalent width at close galactocentric radii as compared to the red\ngalaxies. Amongst the blue galaxies, there is a correlation between Mg II\nequivalent width and galactic stellar mass of the host galaxy. We also find\nthat the distribution of Mg II absorption around group galaxies is more\nextended than that for non-group galaxies, and that groups as a whole have more\nextended radial profiles than individual galaxies. Interestingly, these effects\ncan be satisfactorily modeled by a simple superposition of the absorption\nprofiles of individual member galaxies, assuming that these are the same as\nthose of non-group galaxies, suggesting that the group environment may not\nsignificantly enhance or diminish the Mg II absorption of individual galaxies.\nWe show that there is a strong azimuthal dependence of the Mg II absorption\nwithin 50 kpc of inclined disk-dominated galaxies, indicating the presence of a\nstrongly bipolar outflow aligned along the disk rotation axis. There is no\nsignificant dependence of Mg II absorption on the apparent inclination angle of\ndisk-dominated galaxies.", "category": "astro-ph_CO" }, { "text": "Optical and HI properties of isolated galaxies in the 2MIG catalog. I.\n General relationships: We analyze empirical relationships between the optical, near infrared, and HI\ncharacteristics of isolated galaxies from the 2MIG Catalog covering the entire\nsky. Data on morphological types, K_S-, and B-magnitudes, linear diameters, HI\nmasses, and rotational velocities are examined. The regression parameters,\ndispersions, and correlation coefficients are calculated for pairs of these\ncharacteristics. The resulting relationships can be used to test the\nhierarchical theory of galaxy formation through numerous mergers of cold dark\nmatter.", "category": "astro-ph_CO" }, { "text": "Relativistic effects in the power spectrum of the large scale structure: The forthcoming Stage-IV experiments aim to map the large scale structure of\nthe Universe at high precision. The scales explored require a relativistic\ndescription, in addition to statistical tools for their analysis. In this\nthesis, we study the effects of adding relativistic and primordial\nnon-Gaussianity contributions to the power spectrum. We begin by reviewing the\nstandard cosmology, then we present the cosmological and Newtonian perturbation\ntheory, which are necessary mathematical tools in the computation of our main\nresults. Afterwards we present the main contributions to this thesis. First, we\npresent solutions to the Einstein equations in the long-wavelength\napproximation, this allow us to obtain expressions for the relativistic density\npower spectrum at second and third order, these expressions also include\ncontributions from primordial non-Gaussianity, in terms of the parameters\n$f_{\\mathrm{NL}}$ and $g_{\\mathrm{NL}}$. These results are complemented with\nthe well known Newtonian solutions for the density contrast and are used in the\ncomputation of the total (relativistic + Newtonian) one-loop power spectrum.\nFor completeness we also calculate the bispectrum at tree-level. We discuss the\npossibility of these relativistic effects being detectable with the future\nsurveys considering different limiting values for $f_{\\mathrm{NL}}$ and\n$g_{\\mathrm{NL}}$. Subsequently, we compute the real space galaxy power\nspectrum, including relativistic and primordial non-Gaussianity effects. These\neffects come from the relativistic one-loop power spectrum terms and from\nfactors of the non-linear bias parameter $b_{\\mathrm{NL}}$. We use our\nmodelling to assess the ability of Stage-IV surveys to constrain primordial\nnon-Gaussianity. Finally, we show how this non-linear bias parameter can\neffectively renormalize diverging relativistic contributions at large scales.", "category": "astro-ph_CO" }, { "text": "Deep Chandra observation of the galaxy cluster WARPJ1415.1+3612 at z=1:\n an evolved cool-core cluster at high-redshift: Using the deepest (370 ksec) Chandra observation of a high-redshift galaxy\ncluster, we perform a detailed characterization of the intra-cluster medium\n(ICM) of WARPJ1415.1+3612 at z=1.03. We also explore the connection between the\nICM core properties and the radio/optical properties of the brightest cluster\ngalaxy (BCG). We perform a spatially resolved analysis of the ICM to obtain\ntemperature, metallicity and surface brightness profiles. Using the deprojected\ntemperature and density profiles we accurately derive the cluster mass at\ndifferent overdensities. In addition to the X-ray data, we use archival radio\nVLA imaging and optical GMOS spectroscopy of the central galaxy to investigate\nthe feedback between the central galaxy and the ICM. The X-ray spectral\nanalysis shows a significant temperature drop towards the cluster center, with\na projected value of Tc = 4.6 \\pm 0.4 keV, and a remarkably high central iron\nabundance peak, Zc= 3.6 Zsun. The central cooling time is shorter than 0.1 Gyr\nand the entropy is equal to 9.9 keV cm2. We detect a strong [OII] emission line\nin the optical spectra of the BCG with an equivalent width of -25 \\AA, for\nwhich we derive a star formation rate within the range 2 - 8 Msun/yr. The VLA\ndata reveals a central radio source coincident with the BCG and a faint\none-sided jet-like feature with an extent of 80 kpc. The analysis presented\nshows that WARPJ1415 has a well developed cool core with ICM properties similar\nto those found in the local Universe. Its properties and the clear sign of\nfeedback activity found in the central galaxy in the optical and radio bands,\nshow that feedback processes are already established at z~1. In addition, the\npresence of a strong metallicity peak shows that the central regions have been\npromptly enriched by star formation processes in the central galaxy already at\nz > 1.", "category": "astro-ph_CO" }, { "text": "HerMES: dust attenuation and star formation activity in UV-selected\n samples from z~4 to z~1.5: We study the link between observed ultraviolet luminosity, stellar mass, and\ndust attenuation within rest-frame UV-selected samples at z~ 4, 3, and 1.5. We\nmeasure by stacking at 250, 350, and 500 um in the Herschel/SPIRE images from\nthe HerMES program the average infrared luminosity as a function of stellar\nmass and UV luminosity. We find that dust attenuation is mostly correlated with\nstellar mass. There is also a secondary dependence with UV luminosity: at a\ngiven UV luminosity, dust attenuation increases with stellar mass, while at a\ngiven stellar mass it decreases with UV luminosity. We provide new empirical\nrecipes to correct for dust attenuation given the observed UV luminosity and\nthe stellar mass. Our results also enable us to put new constraints on the\naverage relation between star formation rate and stellar mass at z~ 4, 3, and\n1.5. The star formation rate-stellar mass relations are well described by power\nlaws (SFR~ M^0.7), with the amplitudes being similar at z~4 and z~3, and\ndecreasing by a factor of 4 at z~1.5 at a given stellar mass. We further\ninvestigate the evolution with redshift of the specific star formation rate.\nOur results are in the upper range of previous measurements, in particular at\nz~3, and are consistent with a plateau at 3$=0.0015$, $\\eta(|\\Delta\nz_{\\rm norm}|>0.05)=4\\%$ on a representative test sample at $r<19.8$,\nout-performing currently published estimates. The distributions in narrow\nintervals of magnitudes of the redshifts inferred for the photometric sample\nare in good agreement with the results of tomographic analyses. The inferred\nredshifts also match the photometric redshifts of the redMaPPer galaxy clusters\nfor the probable cluster members. The CNN input and output are available at:\nhttps://deepdip.iap.fr/treyer+2023.", "category": "astro-ph_CO" }, { "text": "Time variation of the Equation of State for Dark Energy: The time variation of the equation of state ($w_Q$) for the dark energy is\nanalyzed by the current values of parameters $\\Omega_Q $, $w_Q $ and their time\nderivatives. In the future, detailed feature of the dark energy could be\nobserved, so we have considered the second derivatives of $w_Q$ for two types\nof potential: One is an inverse power-law type ($V=M^{4+\\alpha}/Q^{\\alpha}$)\nand the other is an exponential one ($V=M^4\\exp{(\\beta M/Q)}$). The first\nderivative $dw_Q/da$ and the second derivative $d^2 w_Q/da^2$ for both\npotentials are derived. The first derivative is estimated by the observed two\nparameters $\\Delta=w_Q+1$ and $\\Omega_Q$, with the assuming for $Q_0$. In the\nlimit $\\Delta \\rightarrow 0$, the first derivative is null and, under the\ntracker approximation, the second derivative also becomes null. For the inverse\npower potential $V=M^{4+\\alpha}/Q^{\\alpha}$, the observed first and second\nderivatives are used to determine the potential parameter $M$ and $\\alpha$. For\nthe potential of $V=M^4\\exp{(\\beta M/Q)}$, the second derivative is estimated\nby the observed parameters $\\Delta$, $\\Omega_Q$ and $dw_Q/da$.", "category": "astro-ph_CO" }, { "text": "Studying the Dynamical Properties of 20 Nearby Galaxy Clusters: Using SDSS-DR7, we construct a sample of 42382 galaxies with redshifts in the\nregion of 20 galaxy clusters. Using two successive iterative methods, the\nadaptive kernel method and the spherical infall model, we obtained 3396\ngalaxies as members belonging to the studied sample. The 2D projected map for\nthe distribution of the clusters members is introduced using the 2D adaptive\nkernel method to get the clusters centers. The cumulative surface number\ndensity profile for each cluster is fitted well with the generalized King\nmodel. The core radii of the clusters' sample are found to vary from 0.18 Mpc\n$\\mbox{h}^{-1}$ (A1459) to 0.47 Mpc $\\mbox{h}^{-1}$ (A2670) with mean value of\n0.295 Mpc $\\mbox{h}^{-1}$.\n The infall velocity profile is determined using two different models, Yahil\napproximation and Praton model. Yahil approximation is matched with the\ndistribution of galaxies only in the outskirts (infall regions) of many\nclusters of the sample, while it is not matched with the distribution within\nthe inner core of the clusters. Both Yahil approximation and Praton model are\nmatched together in the infall region for about 9 clusters in the sample but\nthey are completely unmatched for the clusters characterized by high central\ndensity. For these cluster, Yahil approximation is not matched with the\ndistribution of galaxies, while Praton model can describe well the infall\npattern of such clusters.", "category": "astro-ph_CO" }, { "text": "Precision cosmology from large-scale structure of the Universe: Large scale structure of the Universe becomes a leading source of precision\ncosmological information. We present two particular tools that can be used in\ncosmological analyses of the redshift space galaxy clustering data: a new\nopen-source code CLASS-PT and the theoretical error approach. CLASS-PT computes\none-loop power auto- and cross-power spectra for matter fields and biased\ntracers in real and redshift spaces. We show that the code meets the precision\nstandards set by the upcoming high-precision large-scale structure surveys. The\ntheoretical error likelihood approach allows one to analyze galaxy clustering\ndata without having to measure the scale cut $k_{\\rm max}$. This approach takes\ninto account that theoretical uncertainties affect parameter estimation\ngradually, which helps optimize data analysis and ensures that all available\ncosmological information is extracted.", "category": "astro-ph_CO" }, { "text": "Observational constraints on K-inflation models: We extend the ModeCode software of Mortonson, Peiris and Easther to enable\nnumerical computation of perturbations in K-inflation models, where the scalar\nfield no longer has a canonical kinetic term. Focussing on models where the\nkinetic and potential terms can be separated into a sum, we compute slow-roll\npredictions for various models and use these to verify the numerical code. A\nMarkov chain Monte Carlo analysis is then used to impose constraints from WMAP7\ndata on the addition of a term quadratic in the kinetic energy to the\nLagrangian of simple chaotic inflation models. For a quadratic potential, the\ndata do not discriminate against addition of such a term, while for a quartic\n(\\lambda \\phi^4) potential inclusion of such a term is actually favoured.\nOverall, constraints on such a term from present data are found to be extremely\nweak.", "category": "astro-ph_CO" }, { "text": "Large Scale Anomalies in the Microwave Background: Causation and\n Correlation: Most treatments of large scale anomalies in the microwave sky are a\nposteriori, with unquantified look-elsewhere effects. We contrast these with\nphysical models of specific inhomogeneities in the early universe which then\ngenerate apparent anomalies. Physical models predict correlations between\ncandidate anomalies, as well as the corresponding signals in polarization and\nlarge scale structure, reducing the impact of cosmic variance. We compute the\napparent spatial curvature associated with large-scale inhomogeneities and show\nthat it is typically small, allowing for a self-consistent analysis. Focussing\non a single large plane wave inhomogeneity, we show this can contribute to\nlow-l mode alignment and odd-even asymmetry in the power spectra and the best\nfit inhomogeneity accounts for a significant part of the claimed odd-even\nasymmetry. We argue that this approach can be generalized to provide a more\nquantitative assessment of potential large scale anomalies in the universe.", "category": "astro-ph_CO" }, { "text": "Sample variance, source clustering and their influence on the counts of\n faint radio sources: The shape of the curves defined by the counts of radio sources per unit area\nas a function of their flux density was one of the earliest cosmological\nprobes. Radio source counts continue to be an area of interest, used to study\nthe relative populations of galaxy types in the Universe (as well as\ninvestigate any cosmological evolution in luminosity functions). They are a\nvital consideration for determining how source confusion may limit the depth of\na radio interferometer observation, and are essential for characterising\nextragalactic foregrounds in CMB experiments. There is currently no consensus\nas to the relative populations of the faintest (sub-mJy) source types, where\nthe counts turn-up. Most of the source counts in this regime are gathered from\nmultiple observations that each use a deep, single pointing with a radio\ninterferometer. These independent measurements show large amounts of scatter\n(factors ~ a few) that significantly exceeds their stated uncertainties. In\nthis article we use a simulation of the extragalactic radio continuum emission\nto assess the level at which sample variance may be the cause of the scatter.\nWe find that the scatter induced by sample variance in the simulated counts\ndecreases towards lower flux density bins as the raw source counts increase.\nThe field-to-field variations are significant, and could even be the sole cause\nat >100 {\\mu}Jy. We present a method for evaluating the flux density limit that\na survey must reach in order to reduce the count uncertainty induced by sample\nvariance to a specific value. We also derive a method for correcting Poisson\nerrors on counts in order to include the uncertainties due to the cosmological\nclustering of sources. An empirical constraint on the effect of sample variance\nat these low luminosities is unlikely to arise until the completion of new\nlarge-scale surveys with next-generation radio telescopes.", "category": "astro-ph_CO" }, { "text": "There was movement that was stationary, for the four-velocity had passed\n around: Is the Doppler interpretation of galaxy redshifts in a\nFriedmann-Lemaitre-Robertson-Walker (FLRW) model valid in the context of the\napproach to comoving spatial sections pioneered by de Sitter, Friedmann,\nLemaitre and Robertson, i.e. according to which the 3-manifold of comoving\nspace is characterised by both its curvature and topology? Holonomy\ntransformations for flat, spherical and hyperbolic FLRW spatial sections are\nproposed. By quotienting a simply-connected FLRW spatial section by an\nappropriate group of holonomy transformations, the Doppler interpretation in a\nnon-expanding Minkowski space-time, obtained via four-velocity parallel\ntransport along a photon path, is found to imply that an inertial observer is\nreceding from herself at a speed greater than zero, implying contradictory\nworld-lines. The contradiction in the multiply-connected case occurs for\narbitrary redshifts in the flat and spherical cases, and for certain large\nredshifts in the hyperbolic case. The link between the Doppler interpretation\nof redshifts and cosmic topology can be understood physically as the link\nbetween parallel transport along a photon path and the fact that the comoving\nspatial geodesic corresponding to a photon's path can be a closed loop in an\nFLRW model of any curvature. Closed comoving spatial loops are fundamental to\ncosmic topology.", "category": "astro-ph_CO" }, { "text": "The lack of star formation gradients in galaxy groups up to z~1.6: In the local Universe, galaxy properties show a strong dependence on\nenvironment. In cluster cores, early type galaxies dominate, whereas\nstar-forming galaxies are more and more common in the outskirts. At higher\nredshifts and in somewhat less dense environments (e.g. galaxy groups), the\nsituation is less clear. One open issue is that of whether and how the star\nformation rate (SFR) of galaxies in groups depends on the distance from the\ncentre of mass. To shed light on this topic, we have built a sample of X-ray\nselected galaxy groups at 010^10.3 M_sun in order to have a high spectroscopic\ncompleteness. As we use only spectroscopic redshifts, our results are not\naffected by uncertainties due to projection effects. We use several SFR\nindicators to link the star formation (SF) activity to the galaxy environment.\nTaking advantage of the extremely deep mid-infrared Spitzer MIPS and\nfar-infrared Herschel PACS observations, we have an accurate, broad-band\nmeasure of the SFR for the bulk of the star-forming galaxies. We use\nmulti-wavelength SED fitting techniques to estimate the stellar masses of all\nobjects and the SFR of the MIPS and PACS undetected galaxies. We analyse the\ndependence of the SF activity, stellar mass and specific SFR on the\ngroup-centric distance, up to z~1.6, for the first time. We do not find any\ncorrelation between the mean SFR and group-centric distance at any redshift. We\ndo not observe any strong mass segregation either, in agreement with\npredictions from simulations. Our results suggest that either groups have a\nmuch smaller spread in accretion times with respect to the clusters and that\nthe relaxation time is longer than the group crossing time.", "category": "astro-ph_CO" }, { "text": "Multiple scattering Sunyaev-Zeldovich signal II: relativistic effects: We study the multiple scattering Sunyaev-Zeldovich (SZ) signature, extending\nour previous analysis to high-temperature clusters. We consistently treat the\nanisotropy of the ambient radiation field caused by the first scattering and\nalso consider lowest order kinematic terms. We show that due to temperature\ncorrections monopole through octupole anisotropy of the singly scattered SZ\nsignal attain different spectra in the second scattering. The difference\nbecomes more pronounced at high temperature, and thus could be used to\nconstrain individual line of sight moments of the electron density and\ntemperature profiles. While very challenging from the observational point of\nview, this further extends the list of possible SZ observables that will be\nimportant for 3D cluster-profile reconstruction, possibly helping to break\ngeometric degeneracies caused by projection effects. We also briefly discuss\nthe scattering of primordial CMB anisotropies by SZ clusters.", "category": "astro-ph_CO" }, { "text": "On the ISW-cluster cross-correlation in future surveys: We investigate the cosmological information contained in the\ncross-correlation between the Integrated Sachs-Wolfe (ISW) of the Cosmic\nMicrowave Background (CMB) anisotropy pattern and galaxy clusters from future\nwide surveys. Future surveys will provide cluster catalogues with a number of\nobjects comparable with galaxy catalogues currently used for the detection of\nthe ISW signal by cross-correlation with the CMB anisotropy pattern. By\ncomputing the angular power spectra of clusters and the corresponding\ncross-correlation with CMB, we perform a signal-to-noise ratio (SNR) analysis\nfor the ISW detection as expected from the eROSITA and the Euclid space\nmissions. We discuss the dependence of the SNR of the ISW-cluster\ncross-correlation on the specifications of the catalogues and on the reference\ncosmology. We forecast that the SNRs for ISW-cluster cross-correlation are\nalightly smaller compared to those which can be obtained from future galaxy\nsurveys but the signal is expected to be detected at high significance, i.e.\nmore than $> 3\\,\\sigma$. We also forecast the joint constraints on parameters\nof model extensions of the concordance $\\Lambda$CDM cosmology by combining CMB\nand the ISW-cluster cross-correlation.", "category": "astro-ph_CO" }, { "text": "Constraint on $f(R)$ Gravity through the Redshift Space Distortion: In this paper, a specific family of $f(R)$ models that can produce the\n$\\Lambda$CDM background expansion history is constrained by using the currently\navailable geometric and dynamic probes. The scale dependence of the growth rate\n$f(z,k)$ in this specific family of $f(R)$ model is shown. Therefore to\neliminate the scale dependence of $f\\sigma_8(z)$ in theory, which usually is\ndefined as the product of $f(z,k)$ and $\\sigma_8(z)$, we define\n$f\\sigma_8(z)=d\\sigma_8(z)/d\\ln a$ which is obviously scale independent and\nreproduces the conventional definition in the standard $\\Lambda$CDM cosmology.\nIn doing so, under the assumption that future probes having the same best fit\nvalues as the current ten data points of $f\\sigma_8(z)$, even having $20\\%$\nerror bars enlarged, we find a preliminary constraint\n$f_{R0}=-2.58_{-0.58}^{+2.14}\\times 10^{-6}$ in $1\\sigma$ regions. This\nindicates the great potential that redshift space distortions have in\nconstraining modified gravity theories. We also discuss the nonlinear matter\npower spectrum based on different halo fit models.", "category": "astro-ph_CO" }, { "text": "Cross identification between X-ray and Optical Clusters of Galaxies in\n the SDSS DR7 Field: We use the ROSAT all sky survey X-ray cluster catalogs and the optical SDSS\nDR7 galaxy and group catalogs to cross-identify X-ray clusters with their\noptical counterparts, resulting in a sample of 201 X-ray clusters in the sky\ncoverage of SDSS DR7. We investigate various correlations between the optical\nand X-ray properties of these X-ray clusters, and find that the following\noptical properties are correlated with the X-ray luminosity: the central galaxy\nluminosity, the central galaxy mass, the characteristic group luminosity\n($\\propto \\Lx^{0.43}$), the group stellar mass ($\\propto \\Lx^{0.46}$), with\ntypical 1-$\\sigma$ scatter of $\\sim 0.67$ in $\\log \\Lx$. Using the observed\nnumber distribution of X-ray clusters, we obtain an unbiased scaling relation\nbetween the X-ray luminosity, the central galaxy stellar mass and the\ncharacteristic satellite stellar mass as ${\\log L_X} = -0.26 + 2.90 [\\log\n(M_{\\ast, c} + 0.26 M_{\\rm sat}) -12.0]$ (and in terms of luminosities, as\n${\\log L_X} = -0.15 + 2.38 [\\log (L_{c} + 0.72 L_{\\rm sat}) -12.0]$). We find\nthat the systematic difference between different halo mass estimations, e.g.,\nusing the ranking of characteristic group stellar mass or using the X-ray\nluminosity scaling relation can be used to constrain cosmology. Comparing the\nproperties of groups of similar stellar mass (or optical luminosities) and\nredshift that are X-ray luminous or under-luminous, we find that X-ray luminous\ngroups have more faint satellite galaxies and higher red fraction in their\nsatellites. The cross-identified X-ray clusters together with their optical\nproperties are provided in Appendix B.", "category": "astro-ph_CO" }, { "text": "Constraint on noncommutative spacetime from PLANCK data: We constrain the energy scale of noncommutativity of spacetime using CMB data\nfrom PLANCK. We find that PLANCK data puts the lower bound on the\nnoncommutativity energy scale to about 20 TeV, which is about a factor of two\nlarger than a previous constraint that was obtained using data from WMAP, ACBAR\nand CBI. We further show that inclusion of data of $E$ mode of CMB polarization\nwill not significantly change the constraint.", "category": "astro-ph_CO" }, { "text": "Outflowing Galactic Winds in Post-starburst and AGN Host Galaxies at\n 0.2-2.6$. After\ndecoupling, energy dissipation is due to ambipolar diffusion and decaying MHD\nturbulence, creating a $y$-type distortion. The distortion is completely\ndominated by decaying MHD turbulence, and is of order $y\\approx 10^{-7}$ for a\nfew nG field smoothed over the damping scale at the decoupling epoch,\n$k_{d,dec}\\approx 290 (B_0/1 {\\rm nG})^{-1} {\\rm Mpc}^{-1}$. This contribution\nis as large as those of the known contributions such as reionization and\nvirialized objects at lower redshifts. The projected PIXIE limit on $y$ would\nexclude $B_0>1.0$ and 0.6 nG for $n_B=-2.9$ and -2.3, respectively, and\n$B_0>0.6$ nG for $n_B\\geq 2$. The current limits on the optical depth to\nThomson scattering restrict the predicted $y$-type distortion to be $y\\lesssim\n10^{-8}$. (Abridged)", "category": "astro-ph_CO" }, { "text": "Orbiting Circum-galactic Gas as a Signature of Cosmological Accretion: We use cosmological SPH simulations to study the kinematic signatures of cool\ngas accretion onto a pair of well-resolved galaxy halos. Cold-flow streams and\ngas-rich mergers produce a circum-galactic component of cool gas that generally\norbits with high angular momentum about the galaxy halo before falling in to\nbuild the disk. This signature of cosmological accretion should be observable\nusing background-object absorption line studies as features that are offset\nfrom the galaxy's systemic velocity by ~100 km/s. Accreted gas typically\nco-rotates with the central disk in the form of a warped, extended cold flow\ndisk, such that the observed velocity offset is in the same direction as galaxy\nrotation, appearing in sight lines that avoid the galactic poles. This\nprediction provides a means to observationally distinguish accreted gas from\noutflow gas: the accreted gas will show large one-sided velocity offsets in\nabsorption line studies while radial/bi-conical outflows will not (except\npossibly in special polar projections). This rotation signature has already\nbeen seen in studies of intermediate redshift galaxy-absorber pairs; we suggest\nthat these observations may be among the first to provide indirect\nobservational evidence for cold accretion onto galactic halos. Cold mode halo\ngas typically has ~3-5 times more specific angular momentum than the dark\nmatter. The associated cold mode disk configurations are likely related to\nextended HI/XUV disks seen around galaxies in the local universe. The fraction\nof galaxies with extended cold flow disks and associated offset absorption-line\ngas should decrease around bright galaxies at low redshift, as cold mode\naccretion dies out.", "category": "astro-ph_CO" }, { "text": "Fast radio bursts as a cosmic probe?: We discuss the possibility of using fast radio bursts (FRBs), if\ncosmological, as a viable cosmic probe. We find out that the contribution of\nthe host galaxies to the detected dispersion measures can be inapparent for the\nFRBs not from galaxy centers or star forming regions. The inhomogeneity of the\nintergalactic medium (IGM), however, causes significant deviation of the\ndispersion measure from that predicted in the simplified homogeneous IGM model\nfor individual event. Fortunately, with sufficient FRBs along different\nsightlines but within a very narrow redshift interval (e.g., $\\Delta z \\sim\n0.05$ or $\\Delta z \\sim 0.05(1+z)$), the mean from averaging observed\ndispersion measures does not suffer such a problem and hence may be used as a\ncosmic probe. We show that in the optimistic case (e.g., tens FRBs in each\n$\\Delta z$ have been measured; the most distant FRBs were at redshift $\\geq 3$;\nthe host galaxies and the FRB sources contribute little to the detected\ndispersion measures) and with all the uncertainties (i.e. the inhomogeneity of\nthe IGM, the contribution and uncertainty of host galaxies as well as the\nevolution and error of $f_{\\rm IGM}$) considered, FRBs could help constrain the\nequation of state of dark energy.", "category": "astro-ph_CO" }, { "text": "Inhomogeneous initial conditions for inflation: A wibbly-wobbly\n timey-wimey path to salvation: We use the 3+1 formalism of numerical relativity to investigate the\nrobustness of Starobinsky and Higgs inflation to inhomogeneous initial\nconditions, in the form of either field gradient or kinetic energy density.\nSub-Hubble and Hubble-sized fluctuations generically lead to inflation after an\noscillatory phase between gradient and kinetic energies. Hubble-sized\ninhomogeneities also produce contracting regions that may end up forming\nprimordial black holes, subsequently diluted by inflation. We analyse the\ndynamics of the preinflation era and the generation of vector and tensor\nfluctuations. Our analysis further supports the robustness of inflation to any\nsize of inhomogeneity, in the field, velocity or equation of state. At large\nfield values, the preinflation dynamics only marginally depends on the field\npotential and it is expected that such behaviour is universal and applies to\nany inflation potential of plateau-type, favoured by CMB observations after\nPlanck.", "category": "astro-ph_CO" }, { "text": "Multi-messenger constraints on dark matter annihilation into\n electron-positron pairs: We investigate the production of electrons and positrons in the Milky Way\nwithin the context of dark matter annihilation. Upper limits on the relevant\ncross-section are obtained by combining observational data at different\nwavelengths (from Haslam, WMAP, and Fermi all-sky intensity maps) with recent\nmeasurements of the electron and positron spectra in the solar neighbourhood by\nPAMELA, Fermi, and HESS. We consider synchrotron emission in the radio and\nmicrowave bands, as well as inverse Compton scattering and final-state\nradiation at gamma-ray energies. According to our results, the dark matter\nannihilation cross-section into electron-positron pairs should not be higher\nthan the canonical value for a thermal relic if the mass of the dark matter\ncandidate is smaller than a few GeV. In addition, we also derive a stringent\nupper limit on the inner logarithmic slope, alpha, of the density profile of\nthe Milky Way dark matter halo (alpha < 1 if m_dm < 5 GeV, alpha < 1.3 if m_dm\n< 100 GeV and alpha < 1.5 if m_dm < 2 TeV) assuming that cross-section = 3 x\n10^(-26) cm^3 s(-1). A logarithmic slope steeper than alpha about 1.5 is hardly\ncompatible with a thermal relic lighter than about 1 TeV, regardless of the\ndominant annihilation channel.", "category": "astro-ph_CO" }, { "text": "Analyzing the Hubble tension through hidden sector dynamics in the early\n universe: The recent analysis from the SH0ES Collaboration has confirmed the existence\nof a Hubble tension between measurements at high redshift ($z> 1000$) and at\nlow redshift ($z<1$) at the $5\\sigma$ level with the low redshift measurement\ngiving a higher value. In this work we propose a particle physics model that\ncan help alleviate the Hubble tension via an out-of-equilibrium hidden sector\ncoupled to the visible sector. The particles that populate the dark sector\nconsist of a dark fermion, which acts as dark matter, a dark photon, a massive\nscalar and a massless pseudo-scalar. Assuming no initial population of\nparticles in the dark sector, feeble couplings between the visible and the\nhidden sectors via kinetic mixing populate the dark sector even though the\nnumber densities of hidden sector particles never reach their equilibrium\ndistribution and the two sectors remain at different temperatures. A\ncosmologically consistent analysis is presented where a correlated evolution of\nthe visible and the hidden sectors with coupled Boltzmann equations involving\ntwo temperatures, one for the visible sector and the other for the hidden\nsector, is carried out. The relic density of the dark matter constituted of\ndark fermions is computed in this two-temperature formalism. As a consequence,\nBBN predictions are upheld with a minimal contribution to $\\Delta N_{\\rm eff}$.\nHowever, the out-of-equilibrium decay of the massive scalar to the massless\npseudo-scalar close to the recombination time causes an increase in $\\Delta\nN_{\\rm eff}$ that can help weaken the Hubble tension.", "category": "astro-ph_CO" }, { "text": "The First Stars May Shed Light on Dark Matter: Recent observations of hydrogen absorption that occurred when the first stars\nturned on may give insights into the nature of dark matter.", "category": "astro-ph_CO" }, { "text": "The smearing scale in Laguerre reconstructions of the correlation\n function: To a good approximation, on large cosmological scales the evolved two-point\ncorrelation function of biased tracers is related to the initial one by a\nconvolution. For Gaussian initial conditions, the smearing kernel is Gaussian,\nso if the initial correlation function is parametrized using simple polynomials\nthen the evolved correlation function is a sum of generalized Laguerre\nfunctions of half-integer order. This motivates an analytic Laguerre\nreconstruction algorithm which previous work has shown is fast and accurate.\nThis reconstruction requires as input the width of the smearing kernel. We show\nthat the method can be extended to estimate the width of the smearing kernel\nfrom the same dataset. This estimate, and associated uncertainties, can then be\nused to marginalize over the distribution of reconstructed shapes, and hence\nprovide error estimates on the value of the distance scale which are not tied\nto a particular cosmological model. We also show that if, instead, we\nparametrize the evolved correlation function using simple polynomials, then the\ninitial one is a sum of Hermite polynomials, again enabling fast and accurate\ndeconvolution. If one is willing to use constraints on the smearing scale from\nother datasets, then marginalizing over its value is simpler for Hermite\nreconstruction, potentially providing further speed-up in cosmological\nanalyses.", "category": "astro-ph_CO" }, { "text": "On the Masses of Galaxies in the Local Universe: We compare estimates of stellar mass, Mstar, and dynamical mass,Mdyn,for a\nsample of galaxies from the Sloan Digital Sky Survey (SDSS). We assume\ndynamical homology (i.e., Mdyn = dispersion**2 * Reff, and we find a tight but\nstrongly non-linear relation: the best fit relation is Mstar = Mdyn**0.73, with\nan observed scatter of 0.15 dex. We also find that, at fixed Mstar, the ratio\nMstar/Mdyn depends strongly on galaxy structure, as parameterized by Sersic\nindex, n. The size of the differential effect is on the order of 0.6 dex across\n2 < n < 10. The apparent n-dependence of Mstar/Mdyn is similar to expectations\nfrom simple models, indicating that assuming homology gives the wrong dynamical\nmass. We have also derived dynamical mass estimates that explicitly account for\ndifferences in galaxies' profiles. Using this `structure-corrected' dynamical\nmass estimator, M(dyn,n), the best fit relation is Mstar = M(dyn,n)**(0.92 +-\n0.08) with an observed scatter of 0.13 dex. While the data are thus consistent\nwith a linear relation, they do prefer a slightly shallower slope. Further, we\nsee only a small residual trend in Mstar/M(dyn,n) with n. We find no\nstatistically significant systematic trends in Mstar/M(dyn,n) as a function of\nobserved quantities (e.g, apparent magnitude, redshift), or as a function of\ntracers of stellar populations. The net differential bias in Mstar/M(dyn,n)\nacross a wide range of stellar populations and star formation activities is <=\n0.12 dex. The very good agreement between stellar mass and structure-corrected\ndynamical mass strongly suggests that: 1.) galaxy non-homology has a major\nimpact on dynamical mass estimates, and 2. there are not strong systematic\nbiases in the stellar mass-to-light ratios derived from broadband optical SEDs.\nFurther, these results suggest that that the central dark-to-luminous mass\nratio has a relatively weak mass dependence.", "category": "astro-ph_CO" }, { "text": "Low Masses and High Redshifts: The Evolution of the Mass-Metallicity\n Relation: We present the first robust measurement of the high redshift mass-metallicity\n(MZ) relation at 10^{8}< M/M_{\\sun} < 10^{10}, obtained by stacking spectra of\n83 emission-line galaxies with secure redshifts between 1.3 < z < 2.3. For\nthese redshifts, infrared grism spectroscopy with the Hubble Space Telescope\nWide Field Camera 3 is sensitive to the R23 metallicity diagnostic:\n([OII]3726,3729 + [OIII] 4959,5007)/H\\beta. Using spectra stacked in four mass\nquartiles, we find a MZ relation that declines significantly with decreasing\nmass, extending from 12+log(O/H) = 8.8 at M=10^{9.8} M_{\\sun} to 12+log(O/H)=\n8.2 at M=10^{8.2} M_{\\sun}. After correcting for systematic offsets between\nmetallicity indicators, we compare our MZ relation to measurements from the\nstacked spectra of galaxies with M>10^{9.5} M_{\\sun} and z~2.3. Within the\nstatistical uncertainties, our MZ relation agrees with the z~2.3 result,\nparticularly since our somewhat higher metallicities (by around 0.1 dex) are\nqualitatively consistent with the lower mean redshift z=1.76 of our sample. For\nthe masses probed by our data, the MZ relation shows a steep slope which is\nsuggestive of feedback from energy-driven winds, and a cosmological downsizing\nevolution where high mass galaxies reach the local MZ relation at earlier\ntimes. In addition, we show that our sample falls on an extrapolation of the\nstar-forming main sequence (the SFR-M_{*} relation) at this redshift. This\nresult indicates that grism emission-line selected samples do not have\npreferentially high SFRs. Finally, we report no evidence for evolution of the\nmass-metallicity-SFR plane; our stack-averaged measurements show excellent\nagreement with the local relation.", "category": "astro-ph_CO" }, { "text": "The Effective Theory of Inflation and the Dark Matter Status in the\n Standard Model of the Universe: We present here the effective theory of inflation `a la Ginsburg-Landau in\nwhich the inflaton potential is a polynomial. The slow-roll expansion becomes a\nsystematic 1/N expansion where N ~ 60. The spectral index and the ratio of\ntensor/scalar fluctuations are n_s - 1 = O(1/N), r = O(1/N) while the running\nturns to be d n_s/d \\ln k = O(1/N^2) and can be neglected. The energy scale of\ninflation M ~ 0.7 10^{16} GeV is completely determined by the amplitude of the\nscalar adiabatic fluctuations. A complete analytic study plus the Monte Carlo\nMarkov Chains (MCMC) analysis of the available CMB+LSS data showed: (a) the\nspontaneous breaking of the phi -> - phi symmetry of the inflaton potential.\n(b) a lower bound for r: r > 0.023 (95% CL) and r > 0.046 (68% CL). (c) The\npreferred inflation potential is a double well, even function of the field with\na moderate quartic coupling yielding as most probable values: n_s = 0.964, r =\n0.051. This value for r is within reach of forthcoming CMB observations. We\ninvestigate the DM properties using cosmological theory and the galaxy\nobservations. Our DM analysis is independent of the particle physics model for\nDM and it is based on the DM phase-space density rho_{DM}/sigma^3_{DM}. We\nderive explicit formulas for the DM particle mass m and for the number of\nultrarelativistic degrees of freedom g_d (hence the temperature) at decoupling.\nWe find that m turns to be at the keV scale. The keV scale DM is\nnon-relativistic during structure formation, reproduces the small and large\nscale structure but it cannot be responsible of the e^+ and pbar excess in\ncosmic rays which can be explained by astrophysical mechanisms (Abridged).", "category": "astro-ph_CO" }, { "text": "Euclid Preparation. XXVIII. Forecasts for ten different higher-order\n weak lensing statistics: Recent cosmic shear studies have shown that higher-order statistics (HOS)\ndeveloped by independent teams now outperform standard two-point estimators in\nterms of statistical precision thanks to their sensitivity to the non-Gaussian\nfeatures of large-scale structure. The aim of the Higher-Order Weak Lensing\nStatistics (HOWLS) project is to assess, compare, and combine the constraining\npower of ten different HOS on a common set of $Euclid$-like mocks, derived from\nN-body simulations. In this first paper of the HOWLS series, we computed the\nnontomographic ($\\Omega_{\\rm m}$, $\\sigma_8$) Fisher information for the\none-point probability distribution function, peak counts, Minkowski\nfunctionals, Betti numbers, persistent homology Betti numbers and heatmap, and\nscattering transform coefficients, and we compare them to the shear and\nconvergence two-point correlation functions in the absence of any systematic\nbias. We also include forecasts for three implementations of higher-order\nmoments, but these cannot be robustly interpreted as the Gaussian likelihood\nassumption breaks down for these statistics. Taken individually, we find that\neach HOS outperforms the two-point statistics by a factor of around two in the\nprecision of the forecasts with some variations across statistics and\ncosmological parameters. When combining all the HOS, this increases to a $4.5$\ntimes improvement, highlighting the immense potential of HOS for cosmic shear\ncosmological analyses with $Euclid$. The data used in this analysis are\npublicly released with the paper.", "category": "astro-ph_CO" }, { "text": "Environmental dependence of bulge-dominated galaxy sizes in hierarchical\n models of galaxy formation. Comparison with the local Universe: We compare state-of-the-art semi-analytic models of galaxy formation as well\nas advanced sub-halo abundance matching models with a large sample of\nearly-type galaxies from SDSS at z < 0.3. We focus our attention on the\ndependence of median sizes of central galaxies on host halo mass. The data do\nnot show any difference in the structural properties of early-type galaxies\nwith environment, at fixed stellar mass. All hierarchical models considered in\nthis work instead tend to predict a moderate to strong environmental\ndependence, with the median size increasing by a factor of about 1.5-3 when\nmoving from low to high mass host haloes. At face value the discrepancy with\nthe data is highly significant, especially at the cluster scale, for haloes\nabove log Mhalo > 14. The convolution with (correlated) observational errors\nreduces some of the tension. Despite the observational uncertainties, the data\ntend to disfavour hierarchical models characterized by a relevant contribution\nof disc instabilities to the formation of spheroids, strong gas dissipation in\n(major) mergers, short dynamical friction timescales, and very short quenching\ntimescales in infalling satellites. We also discuss a variety of additional\nrelated issues, such as the slope and scatter in the local size-stellar mass\nrelation, the fraction of gas in local early-type galaxies, and the general\npredictions on satellite galaxies.", "category": "astro-ph_CO" }, { "text": "Pressure Support vs. Thermal Broadening in the Lyman-alpha Forest II:\n Effects of the Equation of State on Transverse Structure: We examine the impact of gas pressure on the transverse coherence of\nhigh-redshift (2 <= z <= 4) Lyman-alpha forest absorption along neighboring\nlines of sight that probe the gas Jeans scale (projected separation Delta r <=\n500 kpc/h comoving; angular separation Delta theta <= 30\"). We compare\npredictions from two smoothed particle hydrodynamics (SPH) simulations that\nhave different photoionization heating rates and thus different\ntemperature-density relations in the intergalactic medium (IGM). We also\ncompare spectra computed from the gas distributions to those computed from the\npressureless dark matter. The coherence along neighboring sightlines is\nmarkedly higher for the hotter, higher pressure simulation, and lower for the\ndark matter spectra. We quantify this coherence using the flux\ncross-correlation function and the conditional distribution of flux decrements\nas a function of transverse and line-of-sight (velocity) separation. Sightlines\nseparated by Delta theta <= 15\" are ideal for probing this transverse\ncoherence. Higher pressure decreases the redshift-space anisotropy of the flux\ncorrelation function, while higher thermal broadening increases the anisotropy.\nIn contrast to the longitudinal (line-of-sight) structure of the Lya forest,\nthe transverse structure on these scales is dominated by pressure effects\nrather than thermal broadening. With the rapid recent growth in the number of\nknown close quasar pairs, paired line-of-sight observations offer a promising\nnew route to probe the IGM temperature-density relation and test the\nunexpectedly high temperatures that have been inferred from single sightline\nanalyses.", "category": "astro-ph_CO" }, { "text": "CMB Polarization Systematics, Cosmological Birefringence and the\n Gravitational Waves Background: Cosmic Microwave Background experiments must achieve very accurate\ncalibration of their polarization reference frame to avoid biasing the\ncosmological parameters. In particular, a wrong or inaccurate calibration might\nmimic the presence of a gravitational wave background, or a signal from\ncosmological birefringence, a phenomenon characteristic of several\nnon-standard, symmetry breaking theories of electrodynamics that allow for\n\\textit{in vacuo} rotation if the polarization direction of the photon.\nNoteworthly, several authors have claimed that the BOOMERanG 2003 (B2K)\npublished polarized power spectra of the CMB may hint at cosmological\nbirefringence. Such analyses, however, do not take into account the reported\ncalibration uncertainties of the BOOMERanG focal plane. We develop a formalism\nto include this effect and apply it to the BOOMERanG dataset, finding a\ncosmological rotation angle $\\alpha=-4.3^\\circ\\pm4.1^\\circ$. We also\ninvestigate the expected performances of future space borne experiment, finding\nthat an overall miscalibration larger then $1^\\circ$ for Planck and $0.2\\circ$\nfor EPIC, if not properly taken into account, will produce a bias on the\nconstraints on the cosmological parameters and could misleadingly suggest the\npresence of a GW background.", "category": "astro-ph_CO" }, { "text": "Dark Sector to Restore Cosmological Concordance: We develop a new phenomenological model that addresses current tensions\nbetween observations of the early and late Universe. Our scenario features: (i)\na decaying dark energy fluid (DDE), which undergoes a transition at $z \\sim\n5,000$, to raise today's value of the Hubble parameter -- addressing the $H_0$\ntension, and (ii) an ultra-light axion (ULA), which starts oscillating at\n$z\\gtrsim 10^4$, to suppress the matter power spectrum -- addressing the $S_8$\ntension. Our Markov Chain Monte Carlo analyses show that such a Dark Sector\nmodel fits a combination of Cosmic Microwave Background (CMB), Baryon Acoustic\nOscillations, and Large Scale Structure (LSS) data slightly better than the\n$\\Lambda$CDM model, while importantly reducing both the $H_0$ and $S_8$\ntensions with late universe probes ($\\lesssim 3\\sigma$). Combined with\nmeasurements from cosmic shear surveys, we find that the discrepancy on $S_8$\nis reduced to the $1.4\\sigma$ level, and the value of $H_0$ is further raised.\nAdding local supernovae measurements, we find that the $H_0$ and $S_8$ tensions\nare reduced to the $1.4\\sigma$ and $1.2\\sigma$ level respectively, with a\nsignificant improvement $\\Delta\\chi^2\\simeq -18$ compared to the $\\Lambda$CDM\nmodel. With this complete dataset, the DDE and ULA are detected at $\\simeq\n4\\sigma$ and $\\simeq2\\sigma$, respectively. We discuss a possible particle\nphysics realization of this model, with a dark confining gauge sector and its\nassociated axion, although embedding the full details within microphysics\nremains an urgent open question. Our scenario will be decisively probed with\nfuture CMB and LSS surveys.", "category": "astro-ph_CO" }, { "text": "AGN feedback in clusters: shock and sound heating: Observations support the view that feedback, in the form of radio outbursts\nfrom active nuclei in central galaxies, prevents catastrophic cooling of gas\nand rapid star formation in many groups and clusters of galaxies. Variations in\njet power drive a succession of weak shocks that can heat regions close to the\nactive galactic nuclei (AGN). On larger scales, shocks fade into sound waves.\nThe Braginskii viscosity determines a well-defined sound damping rate in the\nweakly magnetized intracluster medium (ICM) that can provide sufficient heating\non larger scales. It is argued that weak shocks and sound dissipation are the\nmain means by which radio AGN heat the ICM, in which case, the power spectrum\nof AGN outbursts plays a central role in AGN feedback.", "category": "astro-ph_CO" }, { "text": "A detailed study of the bridge of excess X-ray emission between the\n galaxy clusters Abell 2029 and Abell 2033: We examine Suzaku, XMM-Newton, and Chandra observations of the Abell\n2029/2033 system to investigate the nature of a bridge of X-ray emission\njoining the two galaxy clusters. By modelling the contributions from the\noutskirts of the two clusters, and excluding the emission from the southern\ninfalling group and the background group LOS9, we find a significant excess of\nX-ray emission between the two clusters at the level of 6.5-7.0$\\sigma$,\ndepending on the choice of model, that cannot be explained by the overlap of\nthe clusters. This excess component to the surface brightness is consistent\nwith being emission from a filament with roughly 1.0 Mpc wide. The derived\nemission measure for the gas associated with the filament yields an average gas\ndensity of $3.7^{+1.0}_{-0.7} \\times 10^{-5}$ cm$^{-3}$, corresponding roughly\nto 160 times the mean baryon density of the Universe. The Suzaku X-ray spectrum\nof the excess emission indicates that it is significantly colder\n($1.4_{-0.5}^{+0.7}$ keV) than the cluster outskirts emission from the two\nclusters ($\\sim$ 5 keV), statistically consistent with the temperature expected\nfrom the hottest and densest parts of the warm-hot intergalactic medium (WHIM).\nThe geometry, density, and temperature are similar to those found from X-ray\nstudies of the Abell 222/223 filament.", "category": "astro-ph_CO" }, { "text": "O-V-S-Z and friends: Non-Gaussianity from inhomogeneous reionization: We calculate the cosmic microwave background (CMB) bispectrum due to\ninhomogeneous reionization. We calculate all the terms that can contribute to\nthe bispectrum that are products of first order terms on all scales in\nconformal Newtonian gauge. We also correctly account for the de-correlation\nbetween the matter density and initial conditions using perturbation theory up\nto third order. We find that the bispectrum is of local type as expected. For a\nreasonable model of reionization, in which the Universe is completely ionized\nby redshift z_{ri} ~ 8 with optical depth to the last scattering surface\n\\tau_0=0.087 the signal to noise for detection of the CMB temperature\nbispectrum is S/N ~ 0.1 and confusion in the estimation of primordial\nnon-Gaussianity is f_{NL} ~ -0.1. For an extreme model with z_{ri} ~ 12.5,\n\\tau_0=0.14 we get S/N ~ 0.5 and f_{NL} ~ -0.2.", "category": "astro-ph_CO" }, { "text": "Velocity Bias from the Small Scale Clustering of SDSS-III BOSS Galaxies: We present the measurements and modelling of the projected and redshift-space\nclustering of CMASS galaxies in the Sloan Digital Sky Survey-III Baryon\nOscillation Spectroscopic Survey Data Release 11. For a volume-limited luminous\nred galaxy sample in the redshift range of $0.48=10^5 cm^-3). However, the low-J HCO+ lines (dominating\nthe HCO+ column density) trace less dense (n(H_2)<10^5 cm^-3) and colder\n(T_K<=20 K) gas, whereas the high-J HCO+ emerges from warmer (>30 K) gas than\nthe other molecules.\n The HCO+ J=4-3 line intensity, compared with the lower transition lines and\nwith the HCN J=4-3 line, support the influence of a local XDR environment. The\nestimated N(CN)/N(HCN)~1-4 column density ratios are indicative of an XDR/AGN\nenvironment with a possible contribution of grain-surface chemistry induced by\nX-rays or shocks.", "category": "astro-ph_CO" }, { "text": "The Large-scale Distribution of Cool Gas around Luminous Red Galaxies: We present a measurement of the correlation function between luminous red\ngalaxies and cool gas traced by Mg II \\lambda \\lambda 2796, 2803 absorption, on\nscales ranging from about 30 kpc to 20 Mpc. The measurement is based on\ncross-correlating the positions of about one million red galaxies at z~0.5 and\nthe flux decrements induced in the spectra of about 10^5 background quasars\nfrom the Sloan Digital Sky Survey. We find that: (i) This galaxy-gas\ncorrelation reveals a change of slope on scales of about 1 Mpc, consistent with\nthe expected transition from a dark matter halo dominated environment to a\nregime where clustering is dominated by halo-halo correlations. Assuming that,\non average, the distribution of Mg II gas follows that of dark matter up to a\ngas-to-mass ratio, we find the standard halo model to provide an accurate\ndescription of the gas distribution over three orders of magnitude in scale.\nWithin this framework we estimate the average host halo mass of luminous red\ngalaxies to be about 10^{13.5} M_solar, in agreement with other methods. We\nalso find the Mg II gas-to-mass ratio around LRGs to be consistent with the\ncosmic value estimated on Mpc scales. Combining our galaxy-gas correlation and\nthe galaxy-mass correlation function from galaxy-galaxy lensing analyses we can\ndirectly measure the Mg II gas-to-mass ratio as a function of scale and reach\nthe same conclusion. (ii) From line-width estimates, we show that the velocity\ndispersion of the gas clouds also shows the expected 1- and 2-halo behaviors.\nOn large scales the gas distribution follows the Hubble flow, whereas on small\nscales we observe the velocity dispersion of the Mg II gas clouds to be lower\nthan that of collisionless dark matter particles within their host halo. This\nis in line with the fact that cool clouds are subject to the pressure of the\nvirialized hot gas.", "category": "astro-ph_CO" }, { "text": "Random versus holographic fluctuations of the background metric. II.\n Note on the dark energies arising due to microstructure of space-time: Over the last few years a certain class of dark-energy models decaying\ninversely proportional to the square of the horizon distance emerged on the\nbasis either of Heisenberg uncertainty relations or of the uncertainty relation\nbetween the four-volume and the cosmological constant. The very nature of these\ndark energies is understood to be the same, namely it is the energy of\nbackground space/metric fluctuations. Putting together these uncertainty\nrelations one finds that the model of random fluctuations of the background\nmetric is favored over the holographic one.", "category": "astro-ph_CO" }, { "text": "A detailed view of filaments and sheets in the warm-hot intergalactic\n medium. I. Pancake formation: Numerical simulations predict a considerable fraction of the missing baryons\nat redshift z ~ 0 resting in the so called warm-hot intergalactic medium\n(WHIM). The filaments and sheets of the WHIM have high temperatures 10^5 - 10^7\nK) and a high degree of ionization while having only low to intermediate\ndensities. The particular physical conditions of the WHIM structures, e.g.\ndensity and temperature profiles, velocity fields, are expected to leave their\nspecial imprint on spectroscopic observations. In order to get further insight\ninto these conditions, we perform hydrodynamical simulations of the WHIM.\nInstead of analyzing large simulations of cosmological structure formation, we\nsimulate particular well-defined structures and study the impact of different\nphysical processes as well as of the scale dependencies. We start with the\ncomprehensive study of the one-dimensional collapse (pancake) and examine the\ninfluence of radiative cooling, heating due to an UV background, and thermal\nconduction. We investigate the effect of small scale perturbations given\naccording to the initial cosmological power spectrum. If the initial\nperturbation length scale L exceeds ~ 2 Mpc the collapse leads to shock\nconfined structures. As a result of radiative cooling and of heating due to an\nUV background a relatively cold and dense core forms in the one-dimensional\ncase. The properties of the core (extension, density, and temperature) are\ncorrelated with L. For larger L the core sizes are more concentrated. Thermal\nconduction enhances this trend and may even result in an evaporation of the\ncore. Our estimates predict that a core may start to evaporate for perturbation\nlengths larger than L ~ 30 Mpc. The obtained detailed profiles for density and\ntemperature for prototype WHIM structures allow for the determination of\npossible spectral signatures by the WHIM.", "category": "astro-ph_CO" }, { "text": "Measuring lensing ratios with future cosmological surveys: The ratio between the CMB lensing/galaxy counts and the galaxy shear/galaxy\ncounts cross-correlations combines the information from different cosmological\nprobes to infer cosmographic measurements that are less dependent on\nastrophysical uncertainties and can constrain the geometry of the Universe. We\ndiscuss the future perspectives for the measurement of this lensing ratio as\npreviously introduced, i.e. with the use of the Limber and flat-sky\napproximations and neglecting all the effects on the galaxy survey from\nobserving on the past lightcone. We then show how the cosmological information\nin this estimator is affected by the Limber approximation and by the inclusion\nof the redshift space distorsions (RSD) and magnification lensing contributions\nto the galaxy number counts. We find that the magnification lensing\ncontribution induces a multipole dependence of the lensing ratio that we show\nto be detectable at a statistical significant level combining post-$Planck$ CMB\nsurveys and a Euclid-like experiment. We propose an improved estimator which\ntakes into account this angular scale dependence. Using this extended\nformalism, we present forecasts for upcoming and future cosmological surveys\nand we show at which extent the lensing ratio information can improve the CMB\nconstraints on cosmological parameters. We get that for extended cosmological\nmodels where the neutrino mass, the spatial curvature and the dark energy\nequation of state are allowed to vary, the constraints from $Planck$ on these\nparameters and on $H_0$ can be reduced by $\\sim 40\\%$ with the inclusion of a\nsingle lensing ratio and by $\\sim 60-70\\%$ adding the joint measurement of 9\nlensing ratios with a Euclid-like survey. We also find that neglegcting the\ncontribution from magnification lensing can induce a bias on the derived\ncosmological parameters in a combined analysis.", "category": "astro-ph_CO" }, { "text": "Interferences in the Stochastic Gravitational Wave Background: Although the expansion of the Universe explicitly breaks the time-translation\nsymmetry, cosmological predictions for the stochastic gravitational wave\nbackground (SGWB) are usually derived under the so-called stationary\nhypothesis. By dropping this assumption and keeping track of the time\ndependence of gravitational waves at all length scales, we derive the expected\nunequal-time (and equal-time) waveform of the SGWB generated by scaling\nsources, such as cosmic defects. For extinct and smooth enough sources, we show\nthat all observable quantities are uniquely and analytically determined by the\nholomorphic Fourier transform of the anisotropic stress correlator. Both the\nstrain power spectrum and the energy density parameter are shown to have an\noscillatory fine structure, they significantly differ on large scales while\nrunning in phase opposition at large wavenumbers $k$. We then discuss scaling\nsources that are never extinct nor smooth and which generate a singular Fourier\ntransform of the anisotropic stress correlator. For these, we find the\nappearance of interferences on top of the above-mentioned fine-structure as\nwell as atypical behaviour at small scales. For instance, we expect the\nrescaled strain power spectrum $k^2 \\mathcal{P}_h$ generated by long cosmic\nstrings in the matter era to oscillate around a scale invariant plateau. These\nsingular sources are also shown to produce orders of magnitude difference\nbetween the rescaled strain spectra and the energy density parameter suggesting\nthat only the former should be used for making reliable observable predictions.\nFinally, we discuss how measuring such a fine structure in the SGWB could\ndisambiguate the possible cosmological sources.", "category": "astro-ph_CO" }, { "text": "Diffuse Radio Emission in Abell 754: We present a low frequency study of the diffuse radio emission in the galaxy\ncluster A754. We present new 150 MHz image of the galaxy cluster A754 made with\nthe Giant Metrewave Radio Telescope (GMRT) and discuss the detection of 4\ndiffuse features. We compare the 150 MHz image with the images at 74, 330 and\n1363 MHz; one new diffuse feature is detected. The flux density upperlimits at\n330 and 1363 MHz imply a synchrotron spectral index, $\\alpha > 2$, ($S\\propto\n\\nu^{-\\alpha}$) for the new feature. The 'west relic' detected at 74 MHz\n(Kassim et al 2001) is not detected at 150 MHz and is thus consistent with its\nnon-detection at 1363 MHz (Bacchi et al 2003) and 330 MHz(Kassim et al 2001).\nIntegrated spectra of all the diffuse features are presented. The fourth\ndiffuse feature is located along the proposed merger axis (Zabludoff et al\n1995) in A754 and 0.7 Mpc away from the peak of X-ray emission. We have made\nuse of the framework of adiabatic compression model (Ensslin & Gopal-Krishna\n2001) to obtain spectra. We show that the spectrum of the fourth diffuse\nfeature is consistent with that of a cocoon of a radio galaxy lurking for about\n$9\\times10^{7}$ yr; no shock compression is required. The other three diffuse\nemission have spectra steeper than 1.5 and could be cocoons lurking for longer\ntime. We discuss other possibilities such as shocks and turbulent\nreacceleration being responsible for the diffuse emission in A754.", "category": "astro-ph_CO" }, { "text": "The slope of the Baryonic Tully-Fisher relation: We present the results of a baryonic Tully-Fisher relation (BTFR) study for a\nlocal sample of relatively isolated disk galaxies. We derive a BTFR with a\nslope near 3 measured over about 4 dex in baryon mass for our combined\n\\textrm{H\\,\\scriptsize{I}} and bright spiral disk samples. This BTFR is\nsignificantly flatter and has less scatter than the TFR (stellar mass only)\nwith its slope near 4 reported for other samples and studies. A BTFR slope near\n3 is in better agreement with the expected slope from simple $\\Lambda$CDM\ncosmological simulations that include both stellar and gas baryons. The scatter\nin the TFR/BTFR appears to depend on $W_{20}$: galaxies that rotate slower have\nmore scatter. The atomic gas--to--stars ratio shows a break near $W_{20} = 250$\n\\kms\\, probably associated with a change in star formation efficiency. In\ncontrast the absence of such a break in the BTFR suggests that this relation\nwas probably set at the main epoch of baryon dissipation rather than as a\nproduct of later galactic evolution.", "category": "astro-ph_CO" }, { "text": "The CMB Dipole: Eppur Si Muove: The largest temperature anisotropy in the cosmic microwave background (CMB)\nis the dipole. The simplest interpretation of the dipole is that it is due to\nour motion with respect to the rest frame of the CMB. As well as creating the\n$\\ell$=1 mode of the CMB sky, this motion affects all astrophysical\nobservations by modulating and aberrating sources across the sky. It can be\nseen in galaxy clustering, and in principle its time derivative through a\ndipole-shaped acceleration pattern in quasar positions. Additionally, the\ndipole modulates the CMB temperature anisotropies with the same frequency\ndependence as the thermal Sunyaev-Zeldovich (tSZ) effect and so these modulated\nCMB anisotropies can be extracted from the tSZ maps produced by Planck.\nUnfortunately, this measurement cannot determine if the dipole is due to our\nmotion, but it does provide an independent measure of the dipole and a\nvalidation of the y maps. This measurement, and a description of the\nfirst-order terms of the CMB dipole, are outlined here.", "category": "astro-ph_CO" }, { "text": "Large non-Gaussian Halo Bias from Single Field Inflation: We calculate Large Scale Structure observables for non-Gaussianity arising\nfrom non-Bunch-Davies initial states in single field inflation. These scenarios\ncan have substantial primordial non-Gaussianity from squeezed (but observable)\nmomentum configurations. They generate a term in the halo bias that may be more\nstrongly scale-dependent than the contribution from the local ansatz. We also\ndiscuss theoretical considerations required to generate an observable\nsignature.", "category": "astro-ph_CO" }, { "text": "Improving lensing cluster mass estimate with flexion: Gravitational lensing has long been considered as a valuable tool to\ndetermine the total mass of galaxy clusters. The shear profile as inferred from\nthe statistics of ellipticity of background galaxies allows to probe the\ncluster intermediate and outer regions thus determining the virial mass\nestimate. However, the mass sheet degeneracy and the need for a large number of\nbackground galaxies motivate the search for alternative tracers which can break\nthe degeneracy among model parameters and hence improve the accuracy of the\nmass estimate. Lensing flexion, i.e. the third derivative of the lensing\npotential, has been suggested as a good answer to the above quest since it\nprobes the details of the mass profile. We investigate here whether this is\nindeed the case considering jointly using weak lensing, magnification and\nflexion. We use a Fisher matrix analysis to forecast the relative improvement\nin the mass accuracy for different assumptions on the shear and flexion signal\n- to - noise (S/N) ratio also varying the cluster mass, redshift, and\nellipticity. It turns out that the error on the cluster mass may be reduced up\nto a factor 2 for reasonable values of the flexion S/N ratio. As a general\nresult, we get that the improvement in mass accuracy is larger for more\nflattened haloes, but extracting general trends is a difficult because of the\nmany parameters at play. We nevertheless find that flexion is as efficient as\nmagnification to increase the accuracy in both mass and concentration\ndetermination.", "category": "astro-ph_CO" }, { "text": "Possible Alternate Scenario for short Duration GRBs: In this paper we look at new class of objects made up entirely of dark matter\nparticles. We look at these objects as possible candidate for short duration\ngamma ray bursts eliminating the baryon load problem. These could also provide\na possible scenario for the formation of sub-stellar black holes, distinct from\nthe usual Hawking black hole.", "category": "astro-ph_CO" }, { "text": "Constraints on Primordial Magnetic Fields from Planck combined with the\n South Pole Telescope CMB B-mode polarization measurements: A primordial magnetic field (PMF) present before recombination can leave\nspecific signatures on the cosmic microwave background (CMB) fluctuations. Of\nparticular importance is its contribution to the B-mode polarization power\nspectrum. Indeed, vortical modes sourced by the PMF can dominate the B-mode\npower spectrum on small scales, as they survive damping up to a small fraction\nof the Silk length. Therefore, measurements of the B-mode polarization at\nhigh-$\\ell$ , such as the one recently performed by the South Pole Telescope\n(SPT), have the potential to provide stringent constraints on the PMF. We use\nthe publicly released SPT B-mode polarization spectrum, along with the\ntemperature and polarization data from the Planck satellite, to derive\nconstraints on the magnitude, the spectral index and the energy scale at which\nthe PMF was generated. We find that, while Planck data constrains the magnetic\namplitude to $B_{1 \\, \\text{Mpc}} < 3.3$ nG at 95\\% confidence level (CL), the\nSPT measurement improves the constraint to $B_{1 \\, \\text{Mpc}} < 1.5$ nG. The\nmagnetic spectral index, $n_B$, and the time of the generation of the PMF are\nunconstrained. For a nearly scale-invariant PMF, predicted by simplest\ninflationary magnetogenesis models, the bound from Planck+SPT is $B_{1 \\,\n\\text{Mpc}} < 1.2$ nG at 95% CL. For PMF with $n_B=2$, expected for fields\ngenerated in post-inflationary phase transitions, the 95% CL bound is $B_{1 \\,\n\\text{Mpc}} < 0.002$ nG, corresponding to the magnetic fraction of the\nradiation density $\\Omega_{B\\gamma} < 10^{-3}$ or the effective field $B_{\\rm\neff} < 100$ nG. The patches for the Boltzmann code CAMB and the Markov Chain\nMonte Carlo engine CosmoMC, incorporating the PMF effects on CMB, are made\npublicly available.", "category": "astro-ph_CO" }, { "text": "Testing consistency of general relativity with kinematic and dynamical\n probes: In this work, we test consistency relations between a kinematic probe, the\nobservational Hubble data, and a dynamical probe, the growth rates for cosmic\nlarge scale structure, which should hold if general relativity is the correct\ntheory of gravity on cosmological scales. Moreover, we summarize the\ndevelopment history of parametrization in testings and make an improvement of\nit. Taking advantage of the Hubble parameter given from both parametric and\nnon-parametric methods, we propose three equations and test two of them\nperformed by means of two-dimensional parameterizations, including one using\ntrigonometric functions we propose. As a result, it is found that the\nconsistency relations satisfies well at $1\\sigma$ CL and trigonometric\nfunctions turn out to be efficient tools in parameterizations. Furthermore, in\norder to confirm the validity of our test, we introduce a model of modified\ngravity, DGP model and compare the testing results in the cases of\n$\\Lambda$CDM, \"DGP in GR\" and DGP model with mock data. It can be seen that it\nis the establishing of consistency relations which dominates the results of the\ntesting. Overall, the present observational Hubble data and growth rate data\nfavor convincingly that the general relativity is the correct theory of gravity\non cosmological scales.", "category": "astro-ph_CO" }, { "text": "Testing General Relativity using the Environmental Dependence of Dark\n Matter Halos: In this Letter, we investigate the environmental dependence of dark matter\nhalos in theories that attempt to explain the accelerated expansion of the\nUniverse by modifying general relativity (GR). Using high-resolution N-body\nsimulations in f(R) gravity models which recover GR in dense environments by\nvirtue of the chameleon mechanism, we find a strong environmentally-dependent\ndifference between the lensing mass and dynamical mass estimates of dark matter\nhalos. This environmental dependence of the halo properties can be used as a\nsmoking gun to test GR observationally.", "category": "astro-ph_CO" }, { "text": "The Formation of the Local Group Planes of Galaxies: The confinement of most satellite galaxies in the Local Group to thin planes\npresents a challenge to the theory of hierarchical galaxy clustering. The\nPAndAS collaboration has identified a particularly thin configuration with\nkinematic coherence among companions of M31 and there have been long standing\nclaims that the dwarf companions to the Milky Way lie in a plane roughly\northogonal to the disk of our galaxy. This discussion investigates the possible\norigins of four Local Group planes: the plane similar, but not identical to\nthat identified by PAndAS, an adjacent slightly tilted plane, and two planes\nnear the Milky Way: one with nearer galaxies and the other with more distant\nones. Plausible orbits are found by using a combination of Numerical Action\nmethods and a backward in time integration procedure. For M31, M33, IC10, and\nLeoI, solutions are found that are consistent with measurements of their proper\nmotions. For galaxies in planes, there must be commonalities in their proper\nmotions, and this constraint greatly limits the number of physically plausible\nsolutions. Key to the formation of the planar structures has been the\nevacuation of the Local Void and consequent build-up of the Local Sheet, a wall\nof this void. Most of the M31 companion galaxies were born in early-forming\nfilamentary or sheet-like substrata that chased M31 out of the void. M31 is a\nmoving target because of its attraction toward the Milky Way, and the result\nhas been alignments stretched toward our galaxy. In the case of the\nconfiguration around the Milky Way, it appears that our galaxy was in a\nthree-way competition for companions with M31 and Centaurus A. Only those\nwithin a modest band fell our way. The Milky Ways' attraction toward the Virgo\nCluster resulted in alignments along the Milky Way-Virgo Cluster line.", "category": "astro-ph_CO" }, { "text": "Taxonomy of Dark Energy Models: The accelerated expansion of the Universe is one of the main discoveries of\nthe past decades, indicating the presence of an unknown component: the dark\nenergy. Evidence of its presence is being gathered by a succession of\nobservational experiments with increasing precision in its measurements.\nHowever, the most accepted model for explaining the dynamic of our Universe,\nthe so-called Lambda cold dark matter, face several problems related to the\nnature of such energy component. This has lead to a growing exploration of\nalternative models attempting to solve those drawbacks. In this review, we\nbriefly summarize the characteristics of a (non-exhaustive) list of dark energy\nmodels as well as some of the most used cosmological samples. Next, we discuss\nhow to constrain each model's parameters using observational data. Finally, we\nsummarize the status of dark energy modeling.", "category": "astro-ph_CO" }, { "text": "Reconstructing the Initial Density Field of the Local Universe: Method\n and Test with Mock Catalogs: Our research objective in this paper is to reconstruct an initial linear\ndensity field, which follows the multivariate Gaussian distribution with\nvariances given by the linear power spectrum of the current CDM model and\nevolves through gravitational instability to the present-day density field in\nthe local Universe. For this purpose, we develop a Hamiltonian Markov Chain\nMonte Carlo method to obtain the linear density field from a posterior\nprobability function that consists of two components: a prior of a Gaussian\ndensity field with a given linear spectrum, and a likelihood term that is given\nby the current density field. The present-day density field can be\nreconstructed from galaxy groups using the method developed in Wang et al.\n(2009a). Using a realistic mock SDSS DR7, obtained by populating dark matter\nhaloes in the Millennium simulation with galaxies, we show that our method can\neffectively and accurately recover both the amplitudes and phases of the\ninitial, linear density field. To examine the accuracy of our method, we use\n$N$-body simulations to evolve these reconstructed initial conditions to the\npresent day. The resimulated density field thus obtained accurately matches the\noriginal density field of the Millennium simulation in the density range 0.3 <=\nrho/rho_mean <= 20 without any significant bias. Especially, the Fourier phases\nof the resimulated density fields are tightly correlated with those of the\noriginal simulation down to a scale corresponding to a wavenumber of ~ 1 h/Mpc,\nmuch smaller than the translinear scale, which corresponds to a wavenumber of ~\n0.15 h\\Mpc.", "category": "astro-ph_CO" }, { "text": "Anisotropic Galactic Outflows and Enrichment of the Intergalactic\n Medium. II. Numerical Simulations: We combine an analytic model for anisotropic outflows and galaxy formation\nwith numerical simulations of large-scale structure and halo formation to study\nthe impact of galactic outflows on the evolution of the IGM. We have simulated\nthe evolution of a comoving volume (15 Mpc)^3 in the LCDM universe. We follow\nthe formation of 20000-60000 galaxies and simulate the galactic outflows\nproduced by these galaxies, for five outflow opening angles, alpha=60, 90, 120,\n150, and 180 degrees (isotropic outflows). Anisotropic outflows follow the path\nof least resistance and thus travel preferentially into low-density regions,\naway from cosmological structures where galaxies form. These anisotropic\noutflows are less likely to overlap with one another, or to hit pre-galactic\ncollapsing halos and strip them of their gas, preventing a galaxy from forming.\nGoing from 180 deg to 60 deg, the number of galaxies that actually form\ndoubles, producing twice as many outflows, and these outflows overlap to a\nlesser extent. As a result, the metal volume filling factor of the IGM goes\nfrom 8% for isotropic outflows up to 28% for anisotropic ones. High density\nregions are more efficiently enriched than low density ones (~80% compared to\n~20% by volume), even though most enriched regions are low densities.\nIncreasing the anisotropy of outflows increases the extent of enrichment at all\ndensities, low and high. This is in part because anisotropic outflows are more\nnumerous. When this effect is factored-out, we find that the probability a\ngalaxy will enrich systems at densities up to 10 rho_mean is higher for\nincreasingly anisotropic outflows. This is an effect of the dynamical evolution\nof the IGM. Anisotropic outflows expand preferentially into underdense gas, but\nthat gas can later accrete onto overdense structures.", "category": "astro-ph_CO" }, { "text": "Gravitational energy as dark energy: Average observational quantities: In the timescape scenario cosmic acceleration is understand as an apparent\neffect, due to gravitational energy gradients that grow when spatial curvature\ngradients become significant with the nonlinear growth of cosmic structure.\nThis affects the calibratation of local geometry to the solutions of the\nvolume-average evolution equations corrected by backreaction. In this paper I\ndiscuss recent work on defining observational tests for average geometric\nquantities which can distinguish the timescape model from a cosmological\nconstant or other models of dark energy.", "category": "astro-ph_CO" }, { "text": "Production of EMRIs in Supermassive Black Hole Binaries: We consider the formation of extreme mass-ratio inspirals (EMRIs) sourced\nfrom a stellar cusp centred on a primary supermassive black hole (SMBH) and\nperturbed by an inspiraling less massive secondary SMBH. The problem is\napproached numerically, assuming the stars are non-interacting over these short\ntimescales and performing an ensemble of restricted three-body integrations.\nFrom these simulations we see that not only can EMRIs be produced during this\nprocess, but the dynamics are also quite rich. In particular, most of the EMRIs\nare produced through a process akin to the Kozai-Lidov mechanism, but with\nstrong effects due to the non-Keplerian stellar potential, general relativity,\nand non-secular oscillations in the angular momentum on the orbital timescale\nof the binary SMBH system.", "category": "astro-ph_CO" }, { "text": "The SLUGGS Survey: Globular cluster system kinematics and substructure\n in NGC 4365: We present a kinematic analysis of the globular cluster (GC) system of the\ngiant elliptical galaxy NGC 4365 and find several distinct kinematic\nsubstructures. This analysis is carried out using radial velocities for 269\nGCs, obtained with the DEIMOS instrument on the Keck II telescope as part of\nthe SAGES Legacy Unifying Globulars and Galaxies Survey (SLUGGS). We find that\neach of the three (formerly identified) GC colour subpopulations reveal\ndistinct rotation properties. The rotation of the green GC subpopulation is\nconsistent with the bulk of NGC 4365's stellar light, which `rolls' about the\nphotometric major axis. The blue and red GC subpopulations show `normal'\nrotation about the minor axis. We also find that the red GC subpopulation is\nrotationally dominated beyond 2.5 arcmin (~17 kpc) and that the root mean\nsquared velocity of the green subpopulation declines sharply with radius\nsuggesting a possible bias towards radial orbits relative to the other GC\nsubpopulations. Additionally, we find a population of low velocity GCs that\nform a linear structure running from the SW to the NE across NGC 4365 which\naligns with the recently reported stellar stream towards NGC 4342. These low\nvelocity GCs have g'-i' colours consistent with the overall NGC 4365 GC system\nbut have velocities consistent with the systemic velocity of NGC 4342. We\ndiscuss the possible formation scenarios for the three GC subpopulations as\nwell as the possible origin of the low velocity GC population.", "category": "astro-ph_CO" }, { "text": "A new probe of the small-scale primordial power spectrum: astrometric\n microlensing by ultracompact minihalos: The dark matter enclosed in a density perturbation with a large initial\namplitude (delta-rho/rho > 1e-3) collapses shortly after recombination and\nforms an ultracompact minihalo (UCMH). Their high central densities make UCMHs\nespecially suitable for detection via astrometric microlensing: as the UCMH\nmoves, it changes the apparent position of background stars. A UCMH with a mass\nlarger than a few solar masses can produce a distinctive astrometric\nmicrolensing signal that is detectable by the space astrometry mission Gaia. If\nGaia does not detect gravitational lensing by any UCMHs, then it establishes an\nupper limit on their abundance and constrains the amplitude of the primordial\npower spectrum for k~2700 Mpc^{-1}. These constraints complement the upper\nbound on the amplitude of the primordial power spectrum derived from limits on\ngamma-ray emission from UCMHs because the astrometric microlensing signal\nproduced by an UCMH is maximized if the dark-matter annihilation rate is too\nlow to affect the UCMH's density profile. If dark matter annihilation within\nUCMHs is not detectable, a search for UCMHs by Gaia could constrain the\namplitude of the primordial power spectrum to be less than 1e-5; this bound is\nthree orders of magnitude stronger than the bound derived from the absence of\nprimordial black holes.", "category": "astro-ph_CO" }, { "text": "Discovery of a supercluster in the ZOA in Vela: We report the discovery of a potentially major supercluster that extends\nacross the Galactic Plane in the constellation of Vela, at a mean recessional\nvelocity of ~18,000 km/s. Recent multi-object spectroscopic observations of\nthis Vela Supercluster (VSCL), using AAOmega+2dF and the Southern African Large\nTelescope, confirm an extended galaxy overdensity in the Zone of Avoidance\n(ZOA) located where residual bulk flows predict a considerable mass excess. We\npresent a preliminary analysis of ~4,500 new spectroscopic galaxy redshifts\nobtained in the ZOA centred on the Vela region (l=272.5+-20 deg, b=0+-10 deg).\nThe presently sparsely-sampled dataset traces an overdensity that covers 25 deg\nin Galactic longitude on either side of the Plane, suggesting an extent of 25\ndeg x 20 deg, corresponding to ~115 x 90 $h_{70}$ Mpc at the supercluster\nredshift. In redshift space, the overdensity appears to consist of two merging\nwall-like structures, interspersed with clusters and groups. Both the velocity\nhistogram and the morphology of the multi-branching wall structure are\nconsistent with a supercluster classification. $K_s^o$ galaxy counts show an\nenhancement of ~1.2 over the survey area for galaxies brighter than $M_K^*$ at\nthe VSCL distance, and a galaxy overdensity of $\\delta=0.50\\rm{-}0.77$ within a\nphotometric redshift shell around the VSCL, when compared to various Two-Micron\nAll-Sky Survey samples. Taking account of selection effects, the VSCL is\nestimated to contribute $v_\\rm{LG} \\gtrsim 50$ km/s to the motion of the Local\nGroup.", "category": "astro-ph_CO" }, { "text": "Modified Starobinsky Inflation: Starobinsky has suggested an inflation model which is obtained from the\nvacuum Einstein's equations modified by the one-loop corrections due to\nquantized matter fields. Although the one-loop gravitational action is not\nknown for a general FRW background, it can be obtained in a de Sitter space to\ngive $\\Mp^2 R + \\alpha R^2 + \\beta R^2 \\ln (R/M^2)$. Thus, one needs to\ninvestigate the inflationary behavior of this model compared to the Starobinsky\nmodel (i.e. $\\beta = 0$). The coefficient $\\alpha$ can be changed by varying\nthe renormalization scale $M^2$ and $\\beta$ is obtained from the quantum\nanomaly which is related to the numbers of quantum fields. It has been assumed\nthat $\\alpha \\gg \\beta$. We investigate the viable values of $\\alpha$ and\n$\\beta$ based on the CMB observation. We also scrutinize the reheating process\nin this model.", "category": "astro-ph_CO" }, { "text": "The eROSITA Final Equatorial-Depth Survey (eFEDS): LOFAR view of\n brightest cluster galaxies and AGN feedback: During the performance verification phase of the SRG/eROSITA telescope, the\neROSITA Final Equatorial-Depth Survey (eFEDS) has been carried out. It covers a\n140 deg$^2$ field located at 126$^\\circ <$ R.A. $< 146^\\circ$ and -3$^\\circ <$\nDec. $< +6^\\circ$ with a nominal exposure over the field of 2.2 ks. 542\ncandidate clusters were detected in this field, down to a flux limit $F_X \\sim\n10^{-14}$ erg s$^{-1}$ cm$^{-2}$ in the 0.5-2 keV band. In order to understand\nradio-mode feedback in galaxy clusters, we study the radio emission of\nbrightest cluster galaxies of eFEDS clusters, and we relate it to the X-ray\nproperties of the host cluster. Using LOFAR we identify 227 radio galaxies\nhosted in the BCGs of the 542 galaxy clusters and groups detected in eFEDS. We\ntreat non-detections as radio upper limits. We analyse the properties of radio\ngalaxies, such as redshift and luminosity distribution, offset from the cluster\ncentre, largest linear size and radio power. We study their relation to the\nintracluster medium of the host cluster. We perform statistical tests to deal\nwith upper limits on the radio luminosities. BCGs with radio-loud AGN are more\nlikely to lie close to the cluster centre than radio-quiet BCGs. There is a\nclear relation between the cluster's X-ray luminosity and the radio power of\nthe BCG. Statistical tests indicate that this correlation is not produced by\nselection effects in the radio band. We see no apparent link between largest\nlinear size of the radio galaxy and central density of the host cluster.\nConverting the radio luminosity to kinetic luminosity, we find that radiative\nlosses of the intracluster medium are in an overall balance with the heating\nprovided by the central AGN. Finally, we tentatively classify our objects into\ndisturbed and relaxed, and we show that the link between the AGN and the ICM\napparently holds regardless of the dynamical state of the cluster.", "category": "astro-ph_CO" }, { "text": "Exploring suppressed long-distance correlations as the cause of\n suppressed large-angle correlations: The absence of large-angle correlations in the map of cosmic microwave\nbackground temperature fluctuations is among the well-established anomalies\nidentified in full-sky and cut-sky maps over the past three decades. Suppressed\nlarge-angle correlations are rare statistical flukes in standard inflationary\ncosmological models. One natural explanation could be that the underlying\nprimordial density perturbations lack correlations on large distance scales. To\ntest this idea, we replace Fourier modes by a wavelet basis with compact\nspatial support. While the angular correlation function of perturbations can\nreadily be suppressed, the observed monopole and dipole-subtracted correlation\nfunction is not generally suppressed. This suggests that suppression of\nlarge-angle temperature correlations requires a mechanism that has both\nreal-space and harmonic-space effects.", "category": "astro-ph_CO" }, { "text": "Reconstructing the interaction between dark energy and dark matter using\n Gaussian Processes: We present a nonparametric approach to reconstruct the interaction between\ndark energy and dark matter directly from SNIa Union 2.1 data using Gaussian\nprocesses, which is a fully Bayesian approach for smoothing data. In this\nmethod, once the equation of state ($w$) of dark energy is specified, the\ninteraction can be reconstructed as a function of redshift. For the decaying\nvacuum energy case with $w=-1$, the reconstructed interaction is consistent\nwith the standard $\\Lambda$CDM model, namely, there is no evidence for the\ninteraction. This also holds for the constant $w$ cases from $-0.9$ to $-1.1$\nand for the Chevallier-Polarski-Linder (CPL) parametrization case. If the\nequation of state deviates obviously from $-1$, the reconstructed interaction\nexists at $95\\%$ confidence level. This shows the degeneracy between the\ninteraction and the equation of state of dark energy when they get constraints\nfrom the observational data.", "category": "astro-ph_CO" }, { "text": "Reconstructing the baryon acoustic oscillations using biased tracers: The reconstruction of the initial conditions of the Universe is an important\ntopic in cosmology, particularly in the context of sharpening the measurement\nof the baryon acoustic oscillation (BAO) peak. Nonlinear reconstruction\nalgorithms developed in recent years, when applied to late-time matter fields,\ncan recover to a substantial degree the initial density distribution, however,\nwhen applied to sparse tracers of the matter field, the performance is poorer.\nIn this paper we apply the Shi et al. non-linear reconstruction method to\nbiased tracers in order to establish what factors affect the reconstruction\nperformance. We find that grid resolution, tracer number density and mass\nassignment scheme all have a significant impact on the performance of our\nreconstruction method, with triangular-shaped-cloud (TSC) mass assignment and a\ngrid resolution of ${\\sim}1{-}2h^{-1}$ Mpc being the optimal choice. We also\nshow that our method can be easily adapted to include generic tracer biases up\nto quadratic order in the reconstruction formalism. Applying the reconstruction\nto halo and galaxy samples with a range of tracer number densities, we find\nthat the linear bias is by far the most important bias term, while including\nnonlocal and nonlinear biases only leads to marginal improvements on the\nreconstruction performance. Overall, including bias in the reconstruction\nsubstantially improves the recovery of BAO wiggles, down to\n$k\\sim0.25~h\\text{Mpc}^{-1}$ for tracer number densities between\n$2\\times10^{-4}$ and $2\\times10^{-3}~(h^{-1}\\text{Mpc})^{-3}$.", "category": "astro-ph_CO" }, { "text": "Symmetry of the CMB sky as a new test of its statistical isotropy. Non\n Cosmological Octupole?: In this article we propose a novel test for statistical anisotropy of the\nCMB. The test is based on the fact, that the Galactic foregrounds have a\nremarcably strong symmetry with respect to their antipodal points and with\nrespect to the Galactic plane, while the cosmological signal should not be\nsymmetric or asymmetric under these transitions. We have applied the test for\nthe octupole component of the WMAP ILC 7 map, by looking at a_3,1 and a_3,3,\nand their ratio to a_3,2 both for real and imaginary values. We find abnormal\nsymmetry of the octupole component at the level of 0.58%, compared to Monte\nCarlo simulations. By using the analysis of the phases of the octupole we found\nremarkably strong cross-correlations between the phases of kinematic dipole and\nILC 7 octupole, in full agreement with previous results. We further test the\nmultipole range 2=6\n and the Implications for Reionisation: We present the results of a numerical study comparing photometric and\nphysical properties of simulated z=6-9 galaxies to the observations taken by\nthe WFC3 instrument aboard the Hubble Space Telescope. Using cosmological\nhydrodynamical simulations we find good agreement with observations in\ncolor-color space at all studied redshifts. We also find good agreement between\nobservations and our Schechter luminosity function fit in the observable range,\nMuv<= -18, provided that a moderate dust extinction effect exists for massive\ngalaxies. However beyond what currently can be observed, simulations predict a\nvery large number of low-mass galaxies and evolving steep faint-end slopes from\nalpha_L = -2.15 at z=6 to alpha_L = -2.64 at z=9, with a dependence of\n|alpha_L| \\propto (1+z)^0.59. During the same epoch, the normalization phi*\nincreases and the characteristic magnitude Muv* becomes moderately brighter\nwith decreasing redshift. We find similar trends for galaxy stellar mass\nfunction with evolving low-mass end slope from alpha_M = - 2.26 at z=6 to\nalpha_M = -2.87 at z=9, with a dependence of |alpha_M| \\propto (1+z)^0.65.\nTogether with our recent result on the high escape fraction of ionizing photons\nfor low-mass galaxies, our results suggest that the low-mass galaxies are\nimportant contributor of ionizing photons for the reionisation of the Universe\nat z>=6.", "category": "astro-ph_CO" }, { "text": "Herschel-ATLAS: far-infrared properties of radio-selected galaxies: We use the Herschel-ATLAS science demonstration data to investigate the\nstar-formation properties of radio-selected galaxies in the GAMA-9h field as a\nfunction of radio luminosity and redshift. Radio selection at the lowest radio\nluminosities, as expected, selects mostly starburst galaxies. At higher radio\nluminosities, where the population is dominated by AGN, we find that some\nindividual objects are associated with high far-infrared luminosities. However,\nthe far-infrared properties of the radio-loud population are statistically\nindistinguishable from those of a comparison population of radio-quiet galaxies\nmatched in redshift and K-band absolute magnitude. There is thus no evidence\nthat the host galaxies of these largely low-luminosity (Fanaroff-Riley class\nI), and presumably low-excitation, AGN, as a population, have particularly\nunusual star-formation histories. Models in which the AGN activity in\nhigher-luminosity, high-excitation radio galaxies is triggered by major mergers\nwould predict a luminosity-dependent effect that is not seen in our data (which\nonly span a limited range in radio luminosity) but which may well be detectable\nwith the full Herschel-ATLAS dataset.", "category": "astro-ph_CO" }, { "text": "Beyond the Boost: Measuring the intrinsic dipole of the CMB using the\n spectral distortions of the monopole and quadrupole: We present a general framework for accurate spectral modeling of the low\nmultipoles of the cosmic microwave background (CMB) as observed in a boosted\nframe. In particular, we demonstrate how spectral measurements of the low\nmultipoles can be used to separate the motion-induced dipole of the CMB from a\npossible intrinsic dipole component. In a moving frame, the leakage of an\nintrinsic dipole moment into the CMB monopole and quadrupole induces spectral\ndistortions with distinct frequency functions that respectively peak at 337 GHz\nand 276 GHz. The leakage into the quadrupole moment also induces a geometrical\ndistortion to the spatial morphology of this mode. The combination of these\neffects can be used to lift the degeneracy between the motion-induced dipole\nand any intrinsic dipole that the CMB might possess. Assuming the current\npeculiar velocity measurements, the leakage of an intrinsic dipole with an\namplitude of $\\Delta T = 30\\mu$K into the monopole and quadrupole moments will\nbe detectable by a PIXIE--like experiment at $\\sim 40~$nK ($2.5\\sigma$) and\n$\\sim 130~$nK ($11\\sigma$) level at their respective peak frequencies.", "category": "astro-ph_CO" }, { "text": "Using Cumulative Number Densities to Compare Galaxies across Cosmic Time: Comparing galaxies across redshifts at fixed cumulative number density is a\npopular way to estimate the evolution of specific galaxy populations. This\nmethod ignores scatter in mass accretion histories and galaxy-galaxy mergers,\nwhich can lead to errors when comparing galaxies over large redshift ranges\n(Delta z > 1). We use abundance matching in the LCDM paradigm to estimate the\nmedian change in number density with redshift and provide a simple fit (+0.16\ndex per unit Delta z) for progenitors of z = 0 galaxies. We find that galaxy\ndescendants do not evolve in the same way as galaxy progenitors, largely due to\nscatter in mass accretion histories. We also provide estimates for the 1-sigma\nrange of number densities corresponding to galaxy progenitors and descendants.\nFinally, we discuss some limits on number density comparisons, which arise due\nto difficulties measuring physical quantities (e.g., stellar mass) consistently\nacross redshifts. A public tool to calculate number density evolution for\ngalaxies, as well as approximate halo masses, is available online.", "category": "astro-ph_CO" }, { "text": "Constraints on primordial magnetic fields from the optical depth of the\n cosmic microwave background: Damping of magnetic fields via ambipolar diffusion and decay of\nmagnetohydrodynamical (MHD) turbulence in the post decoupling era heats the\nintergalactic medium (IGM). Delayed recombination of hydrogen atoms in the IGM\nyields an optical depth to scattering of the cosmic microwave background (CMB).\nThe optical depth generated at $z\\gg 10$ does not affect the \"reionization\nbump\" of the CMB polarization power spectrum at low multipoles, but affects the\ntemperature and polarization power spectra at high multipoles. Writing the\npresent-day energy density of fields smoothed over the damping scale at the\ndecoupling epoch as $\\rho_{B,0}=B_{0}^2/2$, we constrain $B_0$ as a function of\nthe spectral index, $n_B$. Using the Planck 2013 likelihood code that uses the\nPlanck temperature and lensing data together with the WMAP 9-year polarization\ndata, we find the 95% upper bounds of $B_0<0.63$, 0.39, and 0.18~nG for\n$n_B=-2.9$, $-2.5$, and $-1.5$, respectively. For these spectral indices, the\noptical depth is dominated by dissipation of the decaying MHD turbulence that\noccurs shortly after the decoupling epoch. Our limits are stronger than the\nprevious limits ignoring the effects of the fields on ionization history.\nInverse Compton scattering of CMB photons off electrons in the heated IGM\ndistorts the thermal spectrum of CMB. Our limits on $B_0$ imply that the\n$y$-type distortion from dissipation of fields in the post decoupling era\nshould be smaller than $10^{-9}$, $4\\times10^{-9}$, and $10^{-9}$,\nrespectively.", "category": "astro-ph_CO" }, { "text": "The cosmic shallows I: interaction of CMB photons in extended galaxy\n halos: We report and analyse the presence of foregrounds in the cosmic microwave\nbackground (CMB) radiation associated to extended galactic halos. Using the\ncross correlation of Planck and WMAP maps and the 2MRS galaxy catalogue, we\nfind that the mean temperature radial profiles around nearby galaxies at $cz\\le\n4500~\\rm{km~s^{-1}}$ show a statistically significant systematic decrease of\n$\\sim 15~\\mu \\rm{K}$ extending up to several galaxy radii. This effect strongly\ndepends on the galaxy morphological type at scales within several tens of times\nthe galaxy size, becoming nearly independent of galaxy morphology at larger\nscales. The effect is significantly stronger for the more extended galaxies,\nwith galaxy clustering having a large impact on the results. Our findings\nindicate the presence of statistically relevant foregrounds in the CMB maps\nthat should be considered in detailed cosmological studies. Besides, we argue\nthat these can be used to explore the intergalactic medium surrounding bright\nlate-type galaxies and allow for diverse astrophysical analyses.", "category": "astro-ph_CO" }, { "text": "The observed galaxy bispectrum from single-field inflation in the\n squeezed limit: Using the consistency relation in Fourier space, we derive the observed\ngalaxy bispectrum from single-field inflation in the squeezed limit, in which\none of the three modes has a wavelength much longer than the other two. This\nprovides a non-trivial check of the full computation of the bispectrum based on\nsecond-order cosmological perturbation theory in this limit. We show that gauge\nmodes need to be carefully removed in the second-order cosmological\nperturbations in order to calculate the observed galaxy bispectrum in the\nsqueezed limit. We then give an estimate of the effective non-Gaussianity due\nto general relativistic lightcone effects that could mimic a primordial\nnon-Gaussian signal.", "category": "astro-ph_CO" }, { "text": "The environment and redshift dependence of accretion onto dark matter\n halos and subhalos: A dark-matter-only Horizon Project simulation is used to investigate the\nenvironment- and redshift- dependence of accretion onto both halos and\nsubhalos. These objects grow in the simulation via mergers and via accretion of\ndiffuse non-halo material, and we measure the combined signal from these two\nmodes of accretion. It is found that the halo accretion rate varies less\nstrongly with redshift than predicted by the Extended Press-Schechter (EPS)\nformalism and is dominated by minor-merger and diffuse accretion events at z=0,\nfor all halos. These latter growth mechanisms may be able to drive the\nradio-mode feedback hypothesised for recent galaxy-formation models, and have\nboth the correct accretion rate and form of cosmological evolution. The low\nredshift subhalo accretors in the simulation form a mass-selected subsample\nsafely above the mass resolution limit that reside in the outer regions of\ntheir host, with ~70% beyond their host's virial radius, where they are\nprobably not being significantly stripped of mass. These subhalos accrete, on\naverage, at higher rates than halos at low redshift and we argue that this is\ndue to their enhanced clustering at small scales. At cluster scales, the mass\naccretion rate onto halos and subhalos at low redshift is found to be only\nweakly dependent on environment and we confirm that at z~2 halos accrete\nindependently of their environment at all scales, as reported by other authors.\nBy comparing our results with an observational study of black hole growth, we\nsupport previous suggestions that at z>1, dark matter halos and their\nassociated central black holes grew coevally, but show that by the present day,\ndark matter halos could be accreting at fractional rates that are up to a\nfactor 3-4 higher than their associated black holes.", "category": "astro-ph_CO" }, { "text": "Performance of Non-Parametric Reconstruction Techniques in the Late-Time\n Universe: In the context of a Hubble tension problem that is growing in its statistical\nsignificance, we reconsider the effectiveness of non-parametric reconstruction\ntechniques which are independent of prescriptive cosmological models. By taking\ncosmic chronometers, Type Ia Supernovae and baryonic acoustic oscillation data,\nwe compare and contrast two important reconstruction approaches, namely\nGaussian processes (GP) and the \\textbf{Lo}cally w\\textbf{e}ighted\n\\textbf{S}catterplot \\textbf{S}moothing together with \\textbf{Sim}ulation and\n\\textbf{ex}trapolation method (LOESS-Simex or LS). In the context of these\nmethods, besides not requiring a cosmological model, they also do not require\nphysical parameters in their approach to their reconstruction of data (but they\ndo depend on statistical hyperparameters). We firstly show how both GP and\nLOESS-Simex can be used to successively reconstruct various data sets to a high\nlevel of precision. We then directly compare both approaches in a quantitative\nmanner by considering several factors, such as how well the reconstructions\napproximate the data sets themselves to how their respective uncertainties\nevolve. In light of the puzzling Hubble tension, it is important to consider\nhow the uncertain regions evolve over redshift and the methods compare for\nestimating cosmological parameters at current times. For cosmic chronometers\nand baryonic acoustic oscillation compiled data sets, we find that GP\ngenerically produce smaller variances for the reconstructed data with a minimum\nvalue of $\\sigma_{\\rm GP-min} = 1.1$, while the situation for LS is totally\ndifferent with a minimum of $\\sigma_{\\rm LS-min} = 50.8$. Moreover, some of\nthese characteristics can be alleviate at low $z$, where LS presents less\nunderestimation in comparison to GP.", "category": "astro-ph_CO" }, { "text": "Extracting the Global 21-cm signal from Cosmic Dawn and Epoch of\n Reionization in the presence of Foreground and Ionosphere: Detection of redshifted \\ion{H}{i} 21-cm emission is a potential probe for\ninvestigating the Universe's first billion years. However, given the\nsignificantly brighter foreground, detecting 21-cm is observationally\ndifficult. The Earth's ionosphere considerably distorts the signal at low\nfrequencies by introducing directional-dependent effects. Here, for the first\ntime, we report the use of Artificial Neural Networks (ANNs) to extract the\nglobal 21cm signal characteristics from the composite all-sky averaged signal,\nincluding foreground and ionospheric effects such as refraction, absorption,\nand thermal emission from the ionosphere's F and D-layers. We assume a\n'perfect' instrument and neglect instrumental calibration and beam effects. To\nmodel the ionospheric effect, we considered the static and time-varying\nionospheric conditions for the mid-latitude region where LOFAR is situated. In\nthis work, we trained the ANN model for various situations using a synthetic\nset of the global 21cm signals created by altering its parameter space based on\nthe \"$\\rm \\tanh$\" parameterized model and the Accelerated Reionization Era\nSimulations (ARES) algorithm. The obtained result shows that the ANN model can\nextract the global signal parameters with an accuracy of $\\ge 96 \\% $ in the\nfinal study when we include foreground and ionospheric effects. On the other\nhand, a similar ANN model can extract the signal parameters from the final\nprediction dataset with an accuracy ranging from $97 \\%$ to $98 \\%$ when\nconsidering more realistic sets of the global 21cm signals based on physical\nmodels.", "category": "astro-ph_CO" }, { "text": "ALMA Observations of SPT-Discovered, Strongly Lensed, Dusty,\n Star-Forming Galaxies: We present Atacama Large Millimeter/submillimeter Array (ALMA) 860 micrometer\nimaging of four high-redshift (z=2.8-5.7) dusty sources that were detected\nusing the South Pole Telescope (SPT) at 1.4 mm and are not seen in existing\nradio to far-infrared catalogs. At 1.5 arcsec resolution, the ALMA data reveal\nmultiple images of each submillimeter source, separated by 1-3 arcsec,\nconsistent with strong lensing by intervening galaxies visible in near-IR\nimaging of these sources. We describe a gravitational lens modeling procedure\nthat operates on the measured visibilities and incorporates\nself-calibration-like antenna phase corrections as part of the model\noptimization, which we use to interpret the source structure. Lens models\nindicate that SPT0346-52, located at z=5.7, is one of the most luminous and\nintensely star-forming sources in the universe with a lensing corrected FIR\nluminosity of 3.7 X 10^13 L_sun and star formation surface density of 4200\nM_sun yr^-1 kpc^-2. We find magnification factors of 5 to 22, with lens\nEinstein radii of 1.1-2.0 arcsec and Einstein enclosed masses of 1.6-7.2x10^11\nM_sun. These observations confirm the lensing origin of these objects, allow us\nto measure the their intrinsic sizes and luminosities, and demonstrate the\nimportant role that ALMA will play in the interpretation of lensed\nsubmillimeter sources.", "category": "astro-ph_CO" }, { "text": "Primordial Non-Gaussianity in the Cosmic Microwave Background: In the last few decades, advances in observational cosmology have given us a\nstandard model of cosmology. We know the content of the universe to within a\nfew percent. With more ambitious experiments on the way, we hope to move beyond\nthe knowledge of what the universe is made of, to why the universe is the way\nit is. In this review paper we focus on primordial non-Gaussianity as a probe\nof the physics of the dynamics of the universe at the very earliest moments. We\ndiscuss 1) theoretical predictions from inflationary models and their\nobservational consequences in the cosmic microwave background (CMB)\nanisotropies; 2) CMB--based estimators for constraining primordial\nnon-Gaussianity with an emphasis on bispectrum templates; 3) current\nconstraints on non-Gaussianity and what we can hope to achieve in the near\nfuture; and 4) non-primordial sources of non-Gaussianities in the CMB such as\nbispectrum due to second order effects, three way cross-correlation between\nprimary-lensing-secondary CMB, and possible instrumental effects.", "category": "astro-ph_CO" }, { "text": "Loop contributions to the scalar power spectrum due to quartic order\n action in ultra slow roll inflation: [Abridged] In contemporary literature, the calculation of modifications to\nthe inflationary scalar power spectrum due to the loops from the higher order\ninteraction terms in the Hamiltonian have led to a discussion regarding the\nvalidity of perturbation theory. Recently, there have been efforts to examine\nthe contributions to the scalar power spectrum due to the loops arising from\nthe cubic order terms in the action describing the perturbations, specifically\nin inflationary scenarios that permit an epoch of ultra slow roll (USR). A\nphase of USR inflation leads to significant observational consequences, such as\nthe copious production of primordial black holes. In this work, we study the\nloop contributions to the scalar power spectrum in a scenario of USR inflation\narising due to the quartic order terms in the action describing the scalar\nperturbations. We compute the loop contributions to the scalar power spectrum\ndue to the dominant term in the action at the quartic order. We consider a\nscenario wherein a phase of USR is sandwiched between two stages of slow roll\ninflation and analyze the behavior of the loop contributions in terms of the\nparameters involved. We examine the late, intermediate and early epochs of USR\nduring inflation. In the inflationary scenario involving a late phase of USR,\nfor reasonable choices of the parameters, we show that the loop corrections are\nnegligible for the entire range of wave numbers. In the intermediate case, the\ncontributions from the loops prove to be scale invariant over large scales, and\nwe find that these contributions can amount to 30% of the leading order power\nspectrum. In the case wherein USR sets in early, we find that the loop\ncontributions could be negative and can dominate the power spectrum at the\nleading order, which indicates a breakdown of the perturbative expansion. We\nconclude with a brief summary and outlook.", "category": "astro-ph_CO" }, { "text": "Explaining Excess Dipole in NVSS Data Using Superhorizon Perturbation: Many observations in recent times have shown evidence against the standard\nassumption of isotropy in the Big Bang model. Introducing a superhorizon scalar\nmetric perturbation has been able to explain some of these anomalies. In this\nwork, we probe the net velocity arising due to the perturbation. We find that\nthis extra component does not contribute to the CMB dipole amplitude while it\ndoes contribute to the dipole in large scale structures. Thus, within this\nmodel's framework, our velocity with respect to the large scale structure is\nnot the same as that extracted from the CMB dipole, assuming it to be of purely\nkinematic origin. Taking this extra velocity component into account, we study\nthe superhorizon mode's implications for the excess dipole observed in the NRAO\nVLA Sky Survey (NVSS). We find that the mode can consistently explain both the\nCMB and NVSS observations. We also find that the model leads to small\ncontributions to the local bulk flow and the dipole in Hubble parameter, which\nare consistent with observations. The model leads to several predictions which\ncan be tested in future surveys. In particular, it implies that the observed\ndipole in large scale structure should be redshift dependent and should show an\nincrease in amplitude with redshift. We also find that the Hubble parameter\nshould show a dipole anisotropy whose amplitude must increase with redshift in\nthe CMB frame. Similar anisotropic behaviour is expected for the observed\nredshift as a function of the luminosity distance.", "category": "astro-ph_CO" }, { "text": "Cosmological backreaction: This work summarises some of the attempts to explain the phenomenon of dark\nenergy as an effective description of complex gravitational physics and the\nproper interpretation of observations. Cosmological backreaction has been shown\nto be relevant for observational (precision) cosmology, nevertheless no\nconvincing explanation of dark energy by means of backreaction has been given\nso far.", "category": "astro-ph_CO" }, { "text": "Unleashing Positive Feedback: Linking the Rates of Star Formation,\n Supermassive Black Hole Accretion and Outflows in Distant Galaxies: Pressure-regulated star formation is a simple variant on the usual\nsupernova-regulated star formation efficiency that controls the global star\nformation rate as a function of cold gas content in star-forming galaxies, and\naccounts for the Schmidt-Kennicutt law in both nearby and distant galaxies.\nInclusion of AGN-induced pressure, by jets and/or winds that flow back onto a\ngas-rich disk, can lead under some circumstances to significantly enhanced star\nformation rates, especially at high redshift and most likely followed by the\nmore widely accepted phase of star formation quenching. Simple expressions are\nderived that relate supermassive black hole growth, star formation and outflow\nrates. The ratios of black hole to spheroid mass and of both black hole\naccretion and outflow rates to star formation rate are predicted as a function\nof time. I suggest various tests of the AGN-triggered star formation\nhypothesis.", "category": "astro-ph_CO" }, { "text": "Flaring Patterns in Blazars: Blazars radiate from relativistic jets launched by a supermassive black hole\nalong our line of sight; the subclass of FSRQs exhibits broad emission lines, a\ntelltale sign of a gas-rich environment and high accretion rate, contrary to\nthe other subclass of the BL Lacertae objects. We show that this dichotomy of\nthe sources in physical properties is enhanced in their flaring activity. The\nBL Lac flares yielded spectral evidence of being driven by further acceleration\nof highly relativistic electrons in the jet. Here we discuss spectral fits of\nmulti-lambda data concerning strong flares of the two flat spectrum radio\nquasars 3C 454.3 and 3C 279 recently detected in gamma rays by the AGILE and\nFermi satellites. We find that optimal spectral fits are provided by external\nCompton radiation enhanced by increasing production of thermal seed photons by\ngrowing accretion. We find such flares to trace patterns on the jet power -\nelectron energy plane that diverge from those followed by flaring BL Lacs, and\ndiscuss why these occur.", "category": "astro-ph_CO" }, { "text": "The origin of the WMAP quadrupole: The cosmic microwave background (CMB) temperature maps from the Wilkinson\nMicrowave Anisotropy Probe (WMAP) are of great importance for cosmology. In\nprevious work we had developed a pipeline for map-making independently of the\nWMAP team. The new maps produced from the WMAP raw data by our pipeline are\nnotably different to the official ones, and the power spectrum as well as the\nbest-fit cosmological parameters are significantly different too. What's more,\nby revealing the inconsistency between the WMAP raw data and their official\nmap, we had pointed out that there must exist an unexpected problem in the WMAP\nteam's pipeline. In this work, we find that the trouble comes from the\ninaccuracy of antenna pointing direction caused by a systematical time drift\nbetween the attitude data and the science data in the WMAP raw time-order data\n(TOD). The CMB quadrupole in the WMAP release can be exactly generated from a\ndifferential dipole field which is completely determined by the spacecraft\nvelocity and the antenna directions without using any CMB signal. After\ncorrecting the WMAP team's error, the CMB quadrupole component disappears.\nTherefore, the released WMAP CMB quadrupole is almost completely artificial and\nthe real quadrupole of the CMB anisotropy should be near zero. Our finding is\nimportant for understanding the early universe.", "category": "astro-ph_CO" }, { "text": "Density Perturbation Growth in Teleparallel Cosmology: We study the cosmological perturbations in teleparallel dark energy models in\nwhich there is a dynamical scalar field with a non-minimal coupling to gravity.\nWe find that the propagating degrees of freedom are the same as in quintessence\ncosmology despite that variables of the perturbed vierbein field are greater\nthan those in metric theories. We numerically show some evident discrepancy\nfrom general relativity in the evolutions of the perturbations on all scales of\nthe universe. We also demonstrate that the gravitational interactions are\nenhanced during the unique tracker evolutions in these models.", "category": "astro-ph_CO" }, { "text": "Testing the Alignment Tendency of Some Polarized Radio Sources: Measuring the alignment of polarized radio sources requires comparing vectors\nat different locations on the sky, i.e. on a sphere. A test of alignment is\nderived herein. While both large scale and coordinate independent, the test\navoids the mathematical subtleties involved when comparing vectors at different\nlocations on a curved surface. Applied to 5442 sources drawn from a published\ncatalog, the analysis finds a level of alignment that would be matched by only\n7% to 14% of data sets with the same sources but with random polarization\ndirections. The locations of the sources involved and the directions that the\nvectors favor and the regions avoided are described as well.", "category": "astro-ph_CO" }, { "text": "Non-Gaussianity of diffuse Galactic synchrotron emission at 408 MHz: Diffuse Galactic emission at low frequencies is a major contaminant for\nstudies of redshifted $21$ cm line studies. Removal of these foregrounds is\nessential for exploiting the signal from neutral hydrogen at high redshifts.\nAnalysis of foregrounds and its characteristics is thus of utmost importance.\nIt is customary to test efficacy of foreground removal techniques using\nsimulated foregrounds. Most simulations assume that the distribution of the\nforeground signal is a Gaussian random field. In this work we test this\nassumption by computing the binned bispectrum for the all-sky $408$ MHz map.\nThis is done by applying different brightness temperature ($T$) thresholds in\norder to assess whether the cooler parts of the sky have different\ncharacteristics. We find that regions with a low brightness temperature $T <\n25$ K indeed have smaller departures from a Gaussian distribution. Therefore,\nthese regions of the sky are ideal for future H{\\sc i} intensity mapping\nsurveys.", "category": "astro-ph_CO" }, { "text": "Spherical collapse model with non-clustering dark energy: We investigate a spherical overdensity model for the non-clustering dark\nenergy (DE) with the constant equation of state, w in a flat universe. In this\ncase, the exact solution for the evolution of the scale factor is obtained for\ngeneral w. We also obtain the exact (when w = - 1/3) and the approximate (when\nw neq -1/3) solutions for the ratio of the overdensity radius to its value at\nthe turnaround epoch (y) for general cosmological parameters. Also the exact\nand approximate solutions of the overdensity at the turnaround epoch (zeta) are\nobtained for general w. Thus, we are able to obtain the non-linear overdensity\nDelta = 1 + delta at any epoch for the given DE model. The non-linear\noverdensity at the virial epoch (Delta_{vir}) is obtained by using the virial\ntheorem and the energy conservation. The non-linear overdensity of every DE\nmodel converges to that of the Einstein de Sitter universe ~ 147 when\nz_{vir}increases. We find that the observed quantities at high redshifts are\ninsensitive to the different w models. The low-redshift cluster (z_{vir} ~\n0.04, i.e., z_{ta} ~ 0.7) shows the most model dependent feature and it should\nbe a suitable object for testing DE models. Also as Omo increases, the model\ndependence of the observed quantities decreases. The error in the approximate\nsolutions is at most 2% for a wide range of the parameter space. Even though\nthe analytic forms of y and \\zeta are obtained for the constant w, they can be\ngeneralized to the slowly varying w. Thus, these analytic forms of the scale\nfactor, y, and zeta provide a very accurate and useful tool for measuring the\nproperties of DE.", "category": "astro-ph_CO" }, { "text": "The Size, Shape and Orientation of Cosmological Voids in the Sloan\n Digital Sky Survey: We present a detailed description of our void finding algorithm which is an\nextension of the prescription by Hoyle and Vogeley (2002). We include a\ndiscussion of the reproducibility and robustness of the algorithm as well as\nthe statistical significance of the detected voids. We apply our void finder to\nthe Data Release 5 (DR5) of the Sloan Digital Sky Survey (SDSS) and identify\n232 cosmological voids. A void catalog which contains the most salient\nproperties of the detected voids is created. We present a statistical analysis\nof the distribution of the size, shape and orientation of our identified\ncosmological voids. We also investigate possible trends with redshift for 0.04\n< z < 0.16. We compare our results to those from an identical analysis of a\nmock catalog based on the LambdaCDM model and find reasonable agreement.\nHowever, some statistically significant differences in the overall orientation\nof cosmological voids are present and will have to be reconciled by further\nrefinement of the simulations.", "category": "astro-ph_CO" }, { "text": "The Origin of Dust in Early-Type Galaxies and Implications for Accretion\n onto Supermassive Black Holes: We have conducted an archival Spitzer study of 38 early-type galaxies (ETGs)\nin order to determine the origin of the dust in approximately half of this\npopulation. Our sample galaxies generally have good wavelength coverage from\n3.6um to 160um, as well as visible-wavelength HST images. We use the Spitzer\ndata to estimate dust masses, or establish upper limits, and find that all of\nthe ETGs with dust lanes in the HST data are detected in all of the Spitzer\nbands and have dust masses of ~10^{5-6.5} Msun, while galaxies without dust\nlanes are not detected at 70um and 160um and typically have <10^5 Msun of dust.\nThe apparently dust-free galaxies do have 24um emission that scales with the\nshorter wavelength flux, yet substantially exceeds the expectations of\nphotospheric emission by approximately a factor of three. We conclude this\nemission is dominated by hot, circumstellar dust around evolved stars that does\nnot survive to form a substantial interstellar component. The order of\nmagnitude variations in dust masses between galaxies with similar stellar\npopulations rules out a subtantial contribution from continual, internal\nproduction in spite of the clear evidence for circumstellar dust. We\ndemonstrate that the interstellar dust is not due to purely external accretion,\nunless the product of the merger rate of dusty satellites and the dust lifetime\nis at least an order of magnitude higher than expected. We propose that dust in\nETGs is seeded by external accretion, yet the accreted dust is maintained by\ncontinued growth in externally-accreted cold gas beyond the nominal lifetime of\nindividual grains. The several Gyr depletion time of the cold gas is long\nenough to reconcile the fraction of dusty ETGs with the merger rate of gas-rich\nsatellites. As the majority of dusty ETGs are also low-luminosity AGN and\nlikely fueled by this cold gas, their lifetime should similarly be several Gyr.", "category": "astro-ph_CO" }, { "text": "Accounting for selection effects in the BH-bulge relations: No evidence\n for cosmological evolution: The redshift evolution of the black hole - bulge relations is an essential\nobservational constraint for models of black hole - galaxy coevolution. In\naddition to the observational challenges for these studies, conclusions are\ncomplicated by the influence of selection effects. We demonstrate that there is\npresently no statistical significant evidence for cosmological evolution in the\nblack hole-bulge relations, once these selection effects are taken into account\nand corrected for. We present a fitting method, based on the bivariate\ndistribution of black hole mass and galaxy property, that accounts for the\nselection function in the fitting and is therefore able to recover the\nintrinsic black hole - bulge relation unbiased. While prior knowledge is\nrestricted to a minimum, we at least require knowledge of either the sample\nselection function and the mass dependence of the active fraction, or the\nspheroid distribution function and the intrinsic scatter in the black hole -\nbulge relation. We employed our fitting routine to existing studies of the\nblack hole-bulge relation at z~1.5 and z~6, using our current best knowledge of\nthe distribution functions. There is no statistical significant evidence for\npositive evolution in the MBH-M* ratio out to z~2. At z~6 the current\nconstraints are less strong, but we demonstrate that the large observed\napparent offset from the local black hole-bulge relation at z~6 is fully\nconsistent with no intrinsic offset. The method outlined here provides a tool\nto obtain more reliable constraints on black hole - galaxy co-evolution in the\nfuture.", "category": "astro-ph_CO" }, { "text": "Enhancing Bispectrum Estimators for Galaxy Redshift Surveys with\n Velocities: We forecast the ability of bispectrum estimators to constrain primordial\nnon-Gaussianity using future photometric galaxy redshift surveys. A full-sky\nsurvey with photometric redshift resolution of $\\sigma_z/(1+z)=0.05$ in the\nredshift range $0.2 72$ km s$^{-1}$ Mpc$^{-1}$\nas many late-time observations indicate, an alternative solution to the Hubble\ntrouble is needed. Lastly, we limited the fraction of relativistic dark matter\nat the matter-radiation equality to be at most 1\\%.", "category": "astro-ph_CO" }, { "text": "Nonstandard cosmology: Considering radial geodesics in the Robertson-Walker metric leads us to\nabandon the co-moving coordinates. Instead we work in the cosmic rest frame.\nSince then the matter is in motion, the solution of Einstein's equations is\nmore complicated. We calculate the first correction to standard cosmology which\nhas an off-diagonal term b dt dr in the metric. It describes the late universe.\nWe then solve Maxwell's equations in the new metric and discuss redshift and\nluminosities. We obtain the correct age of the universe T=14 Gyr= 1/H, without\nassuming a cosmological constant.", "category": "astro-ph_CO" }, { "text": "An ALMA survey of submillimetre galaxies in the Extended Chandra Deep\n Field South: High resolution 870um source counts: We report the first counts of faint submillimetre galaxies (SMG) in the\n870-um band derived from arcsecond resolution observations with the Atacama\nLarge Millimeter Array (ALMA). We have used ALMA to map a sample of 122\n870-um-selected submillimetre sources drawn from the (0.5x0.5)deg^2 LABOCA\nExtended Chandra Deep Field South Submillimetre Survey (LESS). These ALMA maps\nhave an average depth of sigma(870um)~0.4mJy, some ~3x deeper than the original\nLABOCA survey and critically the angular resolution is more than an order of\nmagnitude higher, FWHM of ~1.5\" compared to ~19\" for the LABOCA discovery map.\nThis combination of sensitivity and resolution allows us to precisely pin-point\nthe SMGs contributing to the submillimetre sources from the LABOCA map, free\nfrom the effects of confusion. We show that our ALMA-derived SMG counts broadly\nagree with the submillimetre source counts from previous, lower-resolution\nsingle-dish surveys, demonstrating that the bulk of the submillimetre sources\nare not caused by blending of unresolved SMGs. The difficulty which\nwell-constrained theoretical models have in reproducing the high-surface\ndensities of SMGs, thus remains. However, our observations do show that all of\nthe very brightest sources in the LESS sample, S(870um)>12mJy, comprise\nemission from multiple, fainter SMGs, each with 870-um fluxes of <9mJy. This\nimplies a natural limit to the star-formation rate in SMGs of <10^3 M_Sun/yr,\nwhich in turn suggests that the space densities of z>1 galaxies with gas masses\nin excess of ~5x10^10 M_Sun is <10^-5 Mpc^-3. We also discuss the influence of\nthis blending on the identification and characterisation of the SMG\ncounterparts to these bright submillimetre sources and suggest that it may be\nresponsible for previous claims that they lie at higher redshifts than fainter\nSMGs.", "category": "astro-ph_CO" }, { "text": "Dynamic of the accelerated expansion of the universe in the DGP model: According to experimental data of SNe Ia (Supernovae type Ia), we will\ndiscuss in detial dynamics of the DGP model and introduce a simple\nparametrization of matter $\\omega$, in order to analyze scenarios of the\nexpanding universe and the evolution of the scale factor. We find that the\ndimensionless matter density parameter at the present epoch $\\Omega^0_m=0.3$,\nthe age of the universe $t_0= 12.48$ Gyr,\n$\\frac{a}{a_0}=-2.4e^{\\frac{-t}{25.56}}+2.45$. The next we study the linear\ngrowth of matter perturbations, and we assume a definition of the growth rate,\n$f \\equiv \\frac{dln\\delta}{dlna}$. As many authors for many years, we have been\nusing a good approximation to the growth rate $f \\approx \\Omega^{\\gamma(z)}_m$,\nwe also find that the best fit of the growth index, $\\gamma(z)\\approx 0.687 -\n\\frac{40.67}{1 + e^{1.7. (4.48 + z)}}$, or $\\gamma(z)= 0.667 + 0.033z$ when\n$z\\ll1$. We also compare the age of the universe and the growth index with\nother models and experimental data. We can see that the DGP model describes the\ncosmic acceleration as well as other models that usually refers to dark energy\nand Cold Dark Matter (CDM).", "category": "astro-ph_CO" }, { "text": "Numerical evaluation of inflationary 3-point functions on curved field\n space: We extend the public CppTransport code to calculate the statistical\nproperties of fluctuations in multiple-field inflationary models with curved\nfield space. Our implementation accounts for all physical effects at tree-level\nin the 'in-in' diagrammatic expansion. This includes particle production due to\ntime-varying masses, but excludes scenarios where the curvature perturbation is\ngenerated by averaging over the decay of more than one particle. We test our\nimplementation by comparing results in Cartesian and polar field-space\ncoordinates, showing excellent numerical agreement and only minor degradation\nin compute time. We compare our results with the PyTransport 2.0 code, which\nuses the same computational approach but a different numerical implementation,\nfinding good agreement. Finally, we use our tools to study a class of\ngelaton-like models which could produce an enhanced non-Gaussian signal on\nequilateral configurations of the Fourier bispectrum. We show this is difficult\nto achieve using hyperbolic field-space manifolds and simple inflationary\npotentials.", "category": "astro-ph_CO" }, { "text": "Exploratory X-ray Monitoring of Luminous Radio-Quiet Quasars at High\n Redshift: Initial Results: We present initial results from an exploratory X-ray monitoring project of\ntwo groups of comparably luminous radio-quiet quasars (RQQs). The first\nconsists of four sources at 4.10 <= z <= 4.35, monitored by Chandra, and the\nsecond is a comparison sample of three sources at 1.33 <= z <= 2.74, monitored\nby Swift. Together with archival X-ray data, the total rest-frame temporal\nbaseline spans ~2-4 yr and ~5-13 yr for the first and second group,\nrespectively. Six of these sources show significant X-ray variability over\nrest-frame timescales of ~10^2 - 10^3 d; three of these also show significant\nX-ray variability on rest-frame timescales of ~1-10 d. The X-ray variability\nproperties of our variable sources are similar to those exhibited by nearby and\nfar less luminous active galactic nuclei (AGNs). While we do not directly\ndetect a trend of increasing X-ray variability with redshift, we do confirm\nprevious reports of luminous AGNs exhibiting X-ray variability above that\nexpected from their luminosities, based on simplistic extrapolation from lower\nluminosity sources. This result may be attributed to luminous sources at the\nhighest redshifts having relatively high accretion rates. Complementary\nUV-optical monitoring of our sources shows that variations in their\noptical-X-ray spectral energy distribution are dominated by the X-ray\nvariations. We confirm previous reports of X-ray spectral variations in one of\nour sources, HS 1700+6416, but do not detect such variations in any of our\nother sources in spite of X-ray flux variations of up to a factor of ~4. This\nproject is designed to provide a basic assessment of the X-ray variability\nproperties of RQQs at the highest accessible redshifts that will serve as a\nbenchmark for more systematic monitoring of such sources with future X-ray\nmissions.", "category": "astro-ph_CO" }, { "text": "Primordial magnetic field generation via primordial black hole disks: Large scale primordial magnetic fields (PMFs) threading the intergalactic\nmedium are observed ubiquitously in the Universe playing a key role in the\ncosmic evolution. Their origin is still debated constituting a very active\nfield of research. In the present article, we propose a novel natural ab initio\nmechanism for the origin of such PMFs through the portal of supermassive\nprimordial black holes (PBHs) forming between the Big Bang Nucleosynthesis and\nthe recombination era. In particular, by considering PBHs furnished with a\nlocally isothermal disk we study the generation of a Biermann battery induced\nseed magnetic field (MF) due to the vortexlike motion of the primordial plasma\naround the black hole. Finally, by considering monochromatic PBH mass\ndistributions and deriving the relevant MF power spectrum we make a\nconservative estimate for the seed PMF in intergalactic scales and at redshift\n$z=30$, when typical galaxies are considered to form, which reads as $B\\simeq\n10^{-30}\\mathrm{G}\\left(\\frac{\\ell_\\mathrm{R}}{10^6}\\right)^2\\left(\\frac{M_\\mathrm{PBH}}{10^{14}M_\\odot}\\right)^{5/2}$,\nwhere $M_\\mathrm{PBH}$ is the PBH mass and $\\ell_\\mathrm{R}\\equiv\nR_\\mathrm{d}/R_\\mathrm{ISCO}$, is the ratio of the radius of the disk,\n$R_\\mathrm{d}$ over the radius of the innermost stable circular orbit,\n$R_\\mathrm{ISCO}$. Interestingly enough, by requiring to seed a PMF of the\norder of $10^{-30}\\mathrm{G}$ necessary to give rise to a present day\n$10^{-18}\\mathrm{G}$ in intergalactic scales, we find a lower bound on the PBH\nmass within the range $[10^{10}- 10^{16}]M_\\odot$ depending on the radius of\nthe PBH disk.", "category": "astro-ph_CO" }, { "text": "Apparent Superluminality of Lensed Gravitational Waves: We consider gravitational wave (GW) sources with an associated\nelectromagnetic (EM) counterpart, and analyze the time delay between both\nsignals in the presence of lensing. If GWs have wavelengths comparable to the\nSchwarzschild radius of astrophysical lenses, they must be treated with wave\noptics, whereas EM waves are typically well within the approximation of\ngeometric optics. With concrete examples, we confirm that the GW signal never\narrives before its EM counterpart, if both are emitted at the same time.\nHowever, during the inspiral of a binary, peaks of the GW waveform can arrive\nbefore their EM counterpart. We stress this is only an apparent superluminality\nsince the GW waveform is both distorted and further delayed with respect to\nlight. In any case, measuring the multi-messenger time delay and correctly\ninterpreting it has important implications for unveiling the distribution of\nlenses, testing the nature of gravity, and probing the cosmological expansion\nhistory.", "category": "astro-ph_CO" }, { "text": "Convolution Lagrangian perturbation theory for biased tracers beyond\n general relativity: We compare analytic predictions for real and Fourier space two-point\nstatistics for biased tracers from a variety of Lagrangian Perturbation Theory\napproaches against those from state of the art N-body simulations in $f(R)$\nHu-Sawicki and the nDGP braneworld modified gravity theories.\n We show that the novel physics of gravitational collapse in scalar tensor\ntheories with the chameleon or the Vainshtein screening mechanism can be\neffectively factored in with bias parameters analytically predicted using the\nPeak-Background Split formalism when updated to include the environmental\nsensitivity of modified gravity theories as well as changes to the halo mass\nfunction.\n We demonstrate that Convolution Lagrangian Perturbation Theory (CLPT) and\nStandard Perturbation Theory (SPT) approaches provide accurate analytic methods\nto predict the correlation function and power spectra, respectively, for biased\ntracers in modified gravity models and are able to characterize both the BAO,\npower-law and small scale regimes needed for upcoming galaxy surveys such as\nDESI, Euclid, LSST and WFIRST.", "category": "astro-ph_CO" }, { "text": "Test of cosmic isotropy in the Planck era: The two fundamental assumptions in cosmology are that the Universe is\nstatistically homogeneous and isotropic when averaged on large scales. Given\nthe big implication of these assumptions, there has been a lot of statistical\ntests carried out to verify their validity. Since the first high-precision\nCosmic Microwave Background (CMB) data release by the WMAP satellite, many\nanomalies that challenges the isotropy assumption, including dipolar power\nasymmetry on large angular scales, have been reported. In this talk I will\npresent a brief summary of the test of cosmic isotropy we carried out in the\nlatest WMAP and Planck temperature data.", "category": "astro-ph_CO" }, { "text": "Composition of Low Redshift Halo Gas: Halo gas in low-z (z<0.5) >0.1L* galaxies in high-resolution, large-scale\ncosmological hydrodynamic simulations is examined with respect to three\ncomponents: (cold, warm, hot) with temperatures equal to (<10^5, 10^{5-6},\n>10^6)K, respectively. The warm component is compared, utilizing O VI\n\\lambda\\lambda 1032, 1038 absorption lines, to observations and agreement is\nfound with respect to the galaxy-O VI line correlation, the ratio of O VI line\nincidence rate in blue to red galaxies and the amount of O VI mass in\nstar-forming galaxies. A detailed account of the sources of warm halo gas\n(stellar feedback heating, gravitational shock heating and accretion from the\nintergalactic medium), inflowing and outflowing warm halo gas metallicity\ndisparities and their dependencies on galaxy types and environment is also\npresented. Having the warm component securely anchored, our simulations make\nthe following additional predictions. First, cold gas is the primary component\nin inner regions, with its mass comprising 50% of all gas within\ngalacto-centric radius r=(30,150)kpc in (red, blue) galaxies. Second, at\nr>(30,200)kpc in (red, blue) galaxies the hot component becomes the majority.\nThird, the warm component is a perpetual minority, with its contribution\npeaking at ~30% at r=100-300kpc in blue galaxies and never exceeding 5% in red\ngalaxies. The significant amount of cold gas in low-z early-type galaxies found\nin simulations, in agreement with recent observations (Thom et al.), is\nintriguing, so is the dominance of hot gas at large radii in blue galaxies.", "category": "astro-ph_CO" }, { "text": "Describing variations of the Fisher-matrix across parameter space: Forecasts in cosmology, both with Monte-Carlo Markov-chain methods and with\nthe Fisher matrix formalism, depend on the choice of the fiducial model because\nboth the signal strength of any observable as well as the model nonlinearities\nlinking observables to cosmological parameters vary in the general case. In\nthis paper we propose a method for extrapolating Fisher-forecasts across the\nspace of cosmological parameters by constructing a suitable ba- sis. We\ndemonstrate the validity of our method with constraints on a standard dark\nenergy model extrapolated from a {\\Lambda}CDM-model, as can be expected from\n2-bin weak lensing to- mography with a Euclid-like survey, in the parameter\npairs $(\\Omega_\\text{m},\\sigma_8)$, $(\\Omega_\\text{m}, w_0)$ and $(w_0,\nw_\\text{a})$. Our numerical results include very accurate extrapolations across\na wide range of cosmo- logical parameters in terms of shape, size and\norientation of the parameter likelihood, and a decomposition of the change of\nthe likelihood contours into modes, which are straightforward to interpret in a\ngeometrical way. We find that in particular the variation of the dark energy\nfigure of merit is well captured by our formalism.", "category": "astro-ph_CO" }, { "text": "The effects of baryon physics, black holes and AGN feedback on the mass\n distribution in clusters of galaxies: The spatial distribution of matter in clusters of galaxies is mainly\ndetermined by the dominant dark matter component, however, physical processes\ninvolving baryonic matter are able to modify it significantly. We analyse a set\nof 500 pc resolution cosmological simulations of a cluster of galaxies with\nmass comparable to Virgo, performed with the AMR code RAMSES. We compare the\nmass density profiles of the dark, stellar and gaseous matter components of the\ncluster that result from different assumptions for the subgrid baryonic physics\nand galaxy formation processes. First, the prediction of a gravity only N-body\nsimulation is compared to that of a hydrodynamical simulation with standard\ngalaxy formation recipes, then all results are compared to a hydrodynamical\nsimulation which includes thermal AGN feedback from Super Massive Black Holes\n(SMBH). We find the usual effects of overcooling and adiabatic contraction in\nthe run with standard galaxy formation physics, but very different results are\nfound when implementing SMBHs and AGN feedback. Star formation is strongly\nquenched, producing lower stellar densities throughout the cluster, and much\nless cold gas is available for star formation at low redshifts. At redshift z =\n0 we find a flat density core of radius 10 kpc in both of the dark and stellar\nmatter density profiles. We specu- late on the possible formation mechanisms\nable to produce such cores and we conclude that they can be produced through\nthe coupling of different processes: (I) dynamical friction from the decay of\nblack hole orbits during galaxy mergers; (II) AGN driven gas outflows producing\nfluctuations of the gravitational potential causing the removal of\ncollisionless matter from the central region of the cluster; (III) adiabatic\nexpansion in response to the slow expulsion of gas from the central region of\nthe cluster during the quiescent mode of AGN activity.", "category": "astro-ph_CO" }, { "text": "Distribution function approach to redshift space distortions. Part IV:\n perturbation theory applied to dark matter: We develop a perturbative approach to redshift space distortions (RSD) using\nthe phase space distribution function approach and apply it to the dark matter\nredshift space power spectrum and its moments. RSD can be written as a sum over\ndensity weighted velocity moments correlators, with the lowest order being\ndensity, momentum density and stress energy density. We use standard and\nextended perturbation theory (PT) to determine their auto and cross\ncorrelators, comparing them to N-body simulations. We show which of the terms\ncan be modeled well with the standard PT and which need additional terms that\ninclude higher order corrections which cannot be modeled in PT. Most of these\nadditional terms are related to the small scale velocity dispersion effects,\nthe so called finger of god (FoG) effects, which affect some, but not all, of\nthe terms in this expansion, and which can be approximately modeled using a\nsimple physically motivated ansatz such as the halo model. We point out that\nthere are several velocity dispersions that enter into the detailed RSD\nanalysis with very different amplitudes, which can be approximately predicted\nby the halo model. In contrast to previous models our approach systematically\nincludes all of the terms at a given order in PT and provides a physical\ninterpretation for the small scale dispersion values. We investigate RSD power\nspectrum as a function of \\mu, the cosine of the angle between the Fourier mode\nand line of sight, focusing on the lowest order powers of \\mu and multipole\nmoments which dominate the observable RSD power spectrum. Overall we find\nconsiderable success in modeling many, but not all, of the terms in this\nexpansion.", "category": "astro-ph_CO" }, { "text": "Interplanetary Dust as a Foreground for the LiteBIRD CMB Satellite\n Mission: As ever-more sensitive experiments are made in the quest for primordial CMB B\nModes, the number of potentially significant astrophysical contaminants becomes\nlarger as well. Thermal emission from interplanetary dust, for example, has\nbeen detected by the Planck satellite. While the polarization fraction of this\nZodiacal, or interplanetary dust emission (IPDE) is expected to be low, it is\nbright enough to be detected in total power. Here, estimates of the magnitude\nof the effect as it might be seen by the LiteBIRD satellite are made. The COBE\nIPDE model from Kelsall et al. (1998) is combined with a model of the LiteBIRD\nexperiment's scanning strategy to estimate potential contamination of the CMB\nin both total power and in polarization power spectra. LiteBIRD should detect\nIPDE in temperature across all of its bands, from 40 through 402 GHz, and\nshould improve limits on the polarization fraction of IPDE at the higher end of\nthis frequency range. If the polarization fraction of IPDE is of order 1%, the\ncurrent limit from ISO/CAM measurements in the mid-infrared, it may induce\nlarge-scale polarization B Modes comparable to cosmological models with an r of\norder 0.001. In this case, the polarized IPDE would also need to be modeled and\nremoved. As a CMB foreground, IPDE will always be subdominant to Galactic\nemissions, though because it caused by emission from grains closer to us, it\nappears variable as the Earth travels around the Sun, and may thereby\ncomplicate the data analysis somewhat. But with an understanding of some of the\nsymmetries of the emission and some flexibility in the data processing, it\nshould not be the primary impediment to the CMB polarization measurement.", "category": "astro-ph_CO" }, { "text": "Cospatial 21 cm and metal-line absorbers in the epoch of reionization --\n I : Incidence and observability: Overdense, metal-rich regions, shielded from stellar radiation might remain\nneutral throughout reionization and produce metal as well as 21 cm absorption\nlines. Simultaneous absorption from metals and 21 cm can complement each other\nas probes of underlying gas properties. We use Aurora, a suite of high\nresolution radiation-hydrodynamical simulations of galaxy formation, to\ninvestigate the occurrence of such \"aligned\" absorbers. We calculate absorption\nspectra for 21 cm, OI, CII, SiII and FeII. We find velocity windows with\nabsorption from at least one metal and 21 cm, and classify the aligned\nabsorbers into two categories: 'aligned and cospatial absorbers' and 'aligned\nbut not cospatial absorbers'. While 'aligned and cospatial absorbers' originate\nfrom overdense structures and can be used to trace gas properties, 'aligned but\nnot cospatial absorbers' are due to peculiar velocity effects. The incidence of\nabsorbers is redshift dependent, as it is dictated by the interplay between\nreionization and metal enrichment, and shows a peak at $z \\approx 8$ for the\naligned and cospatial absorbers. While aligned but not cospatial absorbers\ndisappear towards the end of reionization because of the lack of an ambient 21\ncm forest, aligned and cospatial absorbers are associated with overdense\npockets of neutral gas which can be found at lower redshift. We produce mock\nobservations for a set of sightlines for the next generation of telescopes like\nthe ELT and SKA1-LOW, finding that given a sufficiently bright background\nquasar, these telescopes will be able to detect both types of absorbers\nthroughout reionization.", "category": "astro-ph_CO" }, { "text": "The Majority of Compact Massive Galaxies at z~2 are Disk Dominated: We investigate the stellar structure of massive, quiescent galaxies at z~2,\nbased on Hubble Space Telescope/WFC3 imaging from the Early Release Science\nprogram. Our sample of 14 galaxies has stellar masses of M* > 10^{10.8} Msol\nand photometric redshifts of 1.5 < z < 2.5. In agreement with previous work,\ntheir half-light radii are <2 kpc, much smaller than equally massive galaxies\nin the present-day universe. A significant subset of the sample appears highly\nflattened in projection, which implies, considering viewing angle statistics,\nthat a significant fraction of the galaxies in our sample have pronounced\ndisks. This is corroborated by two-dimensional surface brightness profile fits.\nWe estimate that 65% +/- 15% of the population of massive, quiescent z~2\ngalaxies are disk-dominated. The median disk scale length is 1.5 kpc,\nsubstantially smaller than the disks of equally massive galaxies in the\npresent-day universe. Our results provide strong observational evidence that\nthe much-discussed ultra-dense high-redshift galaxies should generally be\nthought of as disk-like stellar systems with the majority of stars formed from\ngas that had time to settle into a disk.", "category": "astro-ph_CO" }, { "text": "Constraining Quasar and IGM Properties Through Bubble Detection in\n Redshifted 21-cm Maps: The infrared detection of a z>7 quasar has opened up a new window to directly\nprobe the IGM during the epoch of reionization. In this paper we theoretically\nconsider the possibility of detecting the ionized bubble around a z=8 quasar\nusing targeted redshifted 21-cm observations with the GMRT. The apparent shape\nand size of the ionized bubble, as seen by a distant observer, depends on the\nparameters \\dot{N}_{phs}/C, x_HI/C and \\tau_Q where \\dot{N}_{phs}, \\tau_Q, x_HI\nand C are respectively the photon emission rate, age of the quasar, the neutral\nfraction and clumping factor of the IGM.Here we have analytically estimated the\nshape and size of a quasar's ionized bubble assuming an uniform IGM and\nignoring other ionizing sources besides the quasar, and used this as a template\nfor matched filter bubble search with the GMRT visibility data. We have assumed\nthat \\dot{N}_{phs} is known from the infrared spectrum and C from theoretical\nconsiderations, which gives us two free parameters x_HI and \\tau_Q for bubble.\nConsidering 1,000 hr of observation, we find that there is a reasonably large\nregion of parameter space where a 3\\sigma detection is possible. We also find\nthat it will be possible to place lower limits on x_HI and \\tau_Q with this\nobservation. Deeper follow up observations can place upper limits on \\tau_Q and\nx_HI. Value of C affect the estimation of x_HI but the estimation of \\tau_Q\nremains unaffected.We have used a semi-numerical technique to simulate the\napparent shape and size of quasar ionized bubbles considering the presence of\nother ionizing sources and inhomogeneities in the IGM. The presence of other\nsources increase the size of the quasar bubble, leading to underestimation of\nx_HI. Clustering of other ionizing sources around the quasar can produce severe\ndistortions in bubble's shape. However, this does not severely affect parameter\nestimation in the bubbles that are large.", "category": "astro-ph_CO" }, { "text": "Empirical predictions for (sub-)millimeter line and continuum deep\n fields: [abridged] Modern (sub-)millimeter/radio interferometers will enable us to\nmeasure the dust and molecular gas emission from galaxies that have\nluminosities lower than the Milky Way, out to high redshifts and with\nunprecedented spatial resolution and sensitivity. This will provide new\nconstraints on the star formation properties and gas reservoir in galaxies\nthroughout cosmic times through dedicated deep field campaigns targeting the\nCO/[CII] lines and dust continuum emission. In this paper, we present empirical\npredictions for such (sub-)millimeter line and continuum deep fields. We base\nthese predictions on the deepest available optical/near-infrared ACS and NICMOS\ndata on the Hubble Ultra Deep Field. Using a physically-motivated spectral\nenergy distribution model, we fit the observed optical/near-infrared emission\nof 13,099 galaxies with redshifts up to z=5, and obtain median likelihood\nestimates of their stellar mass, star formation rate, dust attenuation and dust\nluminosity. We derive statistical constraints on the dust emission in the\ninfrared and (sub-)millimeter which are consistent with the observed\noptical/near-infrared emission in terms of energy balance. This allows us to\nestimate, for each galaxy, the (sub-)millimeter continuum flux densities in\nseveral ALMA, PdBI/NOEMA and JVLA bands. Using empirical relations between the\nobserved CO/[CII] line luminosities and the infrared luminosity, we infer the\nflux of the CO(1-0) and [CII] lines from the estimated infrared luminosity of\neach galaxy in our sample. We then predict the fluxes of higher CO transition\nlines CO(2-1) to CO(7-6) bracketing two extreme gas excitation scenarios. We\nuse our predictions to discuss possible deep field strategies with ALMA. The\npredictions presented in this study will serve as a direct benchmark for future\ndeep field campaigns in the (sub-)millimeter regime.", "category": "astro-ph_CO" }, { "text": "Photometric Calibrations for 21st Century Science: The answers to fundamental science questions in astrophysics, ranging from\nthe history of the expansion of the universe to the sizes of nearby stars,\nhinge on our ability to make precise measurements of diverse astronomical\nobjects. As our knowledge of the underlying physics of objects improves along\nwith advances in detectors and instrumentation, the limits on our capability to\nextract science from measurements is set, not by our lack of understanding of\nthe nature of these objects, but rather by the most mundane of all issues: the\nprecision with which we can calibrate observations in physical units. We stress\nthe need for a program to improve upon and expand the current networks of\nspectrophotometrically calibrated stars to provide precise calibration with an\naccuracy of equal to and better than 1% in the ultraviolet, visible and\nnear-infrared portions of the spectrum, with excellent sky coverage and large\ndynamic range.", "category": "astro-ph_CO" }, { "text": "The optical spectra of X-shaped radio galaxies: X-shaped radio galaxies are defined by their peculiar large-scale radio\nmorphology. In addition to the classical double-lobed structure they have a\npair of low-luminosity wings that straddles the nucleus at almost right angles\nto the active lobes, thus giving the impression of an 'X'. In this paper we\nstudy for the first time the optical spectral properties of this object class\nusing a large sample (~50 sources). We find that the X-shaped radio population\nis composed roughly equally of sources with weak and strong emission line\nspectra, which makes them, in combination with the well-known fact that they\npreferentially have radio powers intermediate between those of Fanaroff-Riley\ntype I (FR I) and type II (FR II) radio galaxies, the archetypal transition\npopulation. We do not find evidence in support of the proposition that the\nX-shape is the result of a recent merger: X-shaped radio sources do not have\nunusually broad emission lines, their nuclear environments are in general not\ndusty, and their host galaxies do not show signs of enhanced star formation.\nInstead, we observe that the nuclear regions of X-shaped radio sources have\nrelatively high temperatures. This finding favours models, which propose that\nthe X-shape is the result of an overpressured environment.", "category": "astro-ph_CO" }, { "text": "Constraints on Cosmographic Functions of Cosmic Chronometers Data Using\n Gaussian Processes: We study observational constraints on the cosmographic functions up to the\nfourth derivative of the scale factor with respect to cosmic time, i.e., the\nso-called snap function, using the non-parametric method of Gaussian Processes.\nAs observational data we use the Hubble parameter data. Also we use mock data\nsets to estimate the future forecast and study the performance of this type of\ndata to constrain cosmographic functions. The combination between a\nnon-parametric method and the Hubble parameter data is investigated as a\nstrategy to reconstruct cosmographic functions. In addition, our results are\nquite general because they are not restricted to a specific type of functional\ndependency of the Hubble parameter. We investigate some advantages of using\ncosmographic functions instead of cosmographic series, since the former are\ngeneral definitions free of approximations. In general, our results do not\ndeviate significantly from $\\Lambda CDM$. We determine a transition redshift\n$z_{tr}=0.637^{+0.165}_{-0.175}$ and $H_{0}=69.45 \\pm 4.34$. Also assuming\npriors for the Hubble constant we obtain $z_{tr}=0.670^{+0.210}_{-0.120}$ with\n$H_{0}=67.44$ (Planck) and $z_{tr}=0.710^{+0.159}_{-0.111}$ with\n$H_{0}=74.03$(SH0ES). Our main results are summarized in table 2.", "category": "astro-ph_CO" }, { "text": "Designing Horndeski and the effective fluid approach: We present a family of designer Horndeski models, i.e. models that have a\nbackground exactly equal to that of the $\\Lambda$CDM model but perturbations\ngiven by the Horndeski theory. Then, we extend the effective fluid approach to\nHorndeski theories, providing simple analytic formulae for the equivalent dark\nenergy effective fluid pressure, density and velocity. We implement the dark\nenergy effective fluid formulae in our code EFCLASS, a modified version of the\nwidely used Boltzmann solver CLASS, and compare the solution of the\nperturbation equations with those of the code hi_CLASS which already includes\nHorndeski models. We find that our simple modifications to the vanilla code are\naccurate to the level of $\\sim 0.1\\%$ with respect to the more complicated\nhi_CLASS code. Furthermore, we study the kinetic braiding model both on and off\nthe attractor and we find that even though the full case has a proper\n$\\Lambda$CDM model limit for large $n$, it is not appropriately smooth, thus\ncausing the quasistatic approximation to break down. Finally, we focus on our\ndesigner model (HDES), which has both a smooth $\\Lambda$CDM limit and\nwell-behaved perturbations, and we use it to perform Markov Chain Monte Carlo\nanalyses to constrain its parameters with the latest cosmological data. We find\nthat our HDES model can also alleviate the soft $2\\sigma$ tension between the\ngrowth data and Planck 18 due to a degeneracy between $\\sigma_8$ and one of its\nmodel parameters that indicates the deviation from the $\\Lambda$CDM model.", "category": "astro-ph_CO" }, { "text": "Ghostly Galaxies as Solitons of Bose-Einstein Dark Matter: The large dark cores of common dwarf galaxies are unexplained by the standard\nheavy particle interpretation of dark matter.\n This puzzle is exacerbated by the discovery of a very large but barely\nvisible, dark matter dominated galaxy Antlia II orbiting the Milky Way,\nuncovered by tracking star motions with the {\\t Gaia} satellite. Although\nAntlia II has a low mass, its visible radius is more than double any known\ndwarf galaxy, with an unprecedentedly low density core. We show that Antlia II\nfavors dark matter as a Bose-Einstein condensate, for which the ground state is\na stable soliton with a core radius given by the de Broglie wavelength. The\nlower the galaxy mass, the larger the de Broglie wavelength, so the least\nmassive galaxies should have the widest soliton cores of lowest density. An\nultra-light boson of $m_\\psi \\sim 1.1 \\times10^{-22}$ eV, accounts well for the\nlarge size and slowly moving stars within Antlia II, and agrees with boson mass\nestimates derived from the denser cores of more massive dwarf galaxies. For\nthis very light boson, Antlia II is close to the lower limiting Jeans scale for\ngalaxy formation permitted by the Uncertainty Principle, so other examples are\nexpected but none significantly larger in size. This simple explanation for the\npuzzling dark cores of dwarf galaxies implies dark matter as an ultra-light\nboson, such as an axion generic in String Theory.", "category": "astro-ph_CO" }, { "text": "Neutrino signals from Neutron Star implosions to Black Holes: We calculate the neutrino luminosity in an astrophysical scenario where dark\nmatter is captured by a neutron star which eventually implodes to form a low\nmass black hole. The Trojan horse scenario involves the collapse of a neutron\nstar (NS) due to the accumulation of a critical amount of dark matter (DM)\nduring its lifetime. As a result, a central disk forms out of the ejected\nmaterial with a finite radial extension, density, temperature, and lepton\nfraction, producing fainter neutrino luminosities and colder associated spectra\nthan found in a regular core-collapse supernova. The emitted gravitational wave\n(GW) signal from the imploding NS should be detectable at ultra-high $\\gtrsim\n0.1$ GHz frequencies.", "category": "astro-ph_CO" }, { "text": "Effect of halo bias and Lyman Limit Systems on the history of cosmic\n reionization: We extend the existing analytical model of reionization by Furlanetto et al.\n(2004) to include the biasing of reionization sources and additional absorption\nby Lyman Limit systems. Our model is, by construction, consistent with the\nobserved evolution of the galaxy luminosity function at z<8 and with the\nobserved evolution of Ly-{\\alpha} forest at z<6. We also find that, for a wide\nrange of values for the relative escape fraction that we consider reasonable,\nand which are consistent with the observational constraints on the relative\nescape fraction from lower redshifts, our reionization model is consistent with\nthe WMAP constraint on the Thompson optical depth and with the SPT and EDGES\nconstraints on the duration of reionization. We, therefore, conclude that it is\npossible to develop physically realistic models of reionization that are\nconsistent with all existing observational constraints.", "category": "astro-ph_CO" }, { "text": "The WiggleZ Dark Energy Survey: measuring the cosmic expansion history\n using the Alcock-Paczynski test and distant supernovae: Astronomical observations suggest that today's Universe is dominated by a\ndark energy of unknown physical origin. One of the most notable consequences in\nmany models is that dark energy should cause the expansion of the Universe to\naccelerate: but the expansion rate as a function of time has proven very\ndifficult to measure directly. We present a new determination of the cosmic\nexpansion history by combining distant supernovae observations with a\ngeometrical analysis of large-scale galaxy clustering within the WiggleZ Dark\nEnergy Survey, using the Alcock-Paczynski test to measure the distortion of\nstandard spheres. Our result constitutes a robust and non-parametric\nmeasurement of the Hubble expansion rate as a function of time, which we\nmeasure with 10-15% precision in four bins within the redshift range 0.1 < z <\n0.9. We demonstrate that the cosmic expansion is accelerating, in a manner\nindependent of the parameterization of the cosmological model (although\nassuming cosmic homogeneity in our data analysis). Furthermore, we find that\nthis expansion history is consistent with a cosmological-constant dark energy.", "category": "astro-ph_CO" }, { "text": "UV-to-FIR analysis of Spitzer/IRAC sources in the Extended Groth Strip\n II: Photometric redshifts, Stellar masses and Star formation rates: Based on the ultraviolet to far-infrared photometry already compiled and\npresented in a companion paper (Barro et al. 2011a, Paper I), we present a\ndetailed SED analysis of nearly 80,000 IRAC 3.6+4.5 micron selected galaxies in\nthe Extended Groth Strip. We estimate photometric redshifts, stellar masses,\nand star formation rates separately for each galaxy in this large sample. The\ncatalog includes 76,936 sources with [3.6] < 23.75 (85% completeness level of\nthe IRAC survey) over 0.48 square degrees. The typical photometric redshift\naccuracy is Delta z/(1+z)=0.034, with a catastrophic outlier fraction of just\n2%. We quantify the systematics introduced by the use of different stellar\npopulation synthesis libraries and IMFs in the calculation of stellar masses.\nWe find systematic offsets ranging from 0.1 to 0.4 dex, with a typical scatter\nof 0.3 dex. We also provide UV- and IR-based SFRs for all sample galaxies,\nbased on several sets of dust emission templates and SFR indicators. We\nevaluate the systematic differences and goodness of the different SFR\nestimations using the deep FIDEL 70 micron data available in the EGS. Typical\nrandom uncertainties of the IR-bases SFRs are a factor of two, with\nnon-negligible systematic effects at z$\\gtrsim$1.5 observed when only MIPS 24\nmicron data is available. All data products (SEDs, postage stamps from imaging\ndata, and different estimations of the photometric redshifts, stellar masses,\nand SFRs of each galaxy) described in this and the companion paper are publicly\navailable, and they can be accessed through our the web-interface utility\nRainbow-navigator", "category": "astro-ph_CO" }, { "text": "Oxford SWIFT IFS and multi-wavelength observations of the Eagle galaxy\n at z=0.77: The `Eagle' galaxy at a redshift of 0.77 is studied with the Oxford Short\nWavelength Integral Field Spectrograph (SWIFT) and multi-wavelength data from\nthe All-wavelength Extended Groth strip International Survey (AEGIS). It was\nchosen from AEGIS because of the bright and extended emission in its slit\nspectrum. Three dimensional kinematic maps of the Eagle reveal a gradient in\nvelocity dispersion which spans 35-75 +/- 10 km/s and a rotation velocity of 25\n+/- 5 km/s uncorrected for inclination. Hubble Space Telescope images suggest\nit is close to face-on. In comparison with galaxies from AEGIS at similar\nredshifts, the Eagle is extremely bright and blue in the rest-frame optical,\nhighly star-forming, dominated by unobscured star-formation, and has a low\nmetallicity for its size. This is consistent with its selection. The Eagle is\nlikely undergoing a major merger and is caught in the early stage of a\nstar-burst when it has not yet experienced metal enrichment or formed the mass\nof dust typically found in star-forming galaxies.", "category": "astro-ph_CO" }, { "text": "Stellar population gradients in the cores of nearby field E+A galaxies: We have selected a sample of local E+A galaxies from the Sloan Digital Sky\nSurvey (SDSS) Data Release 7 for follow up integral field spectroscopy with the\nWide Field Spectrograph (WiFeS) on the ANU 2.3-m telescope. The sample was\nselected using the Halpha line in place of the [OII]3727 line as the indicator\nof on-going star formation (or lack thereof). This allowed us to select a lower\nredshift sample of galaxies than available in the literature since the\n[OII]3727 falls off the blue end of the wavelength coverage in the SDSS for the\nvery lowest redshift objects. This low redshift selection means that the\ngalaxies have a large angular to physical scale which allows us to resolve the\ncentral ~1kpc region of the galaxies; the region where stellar population\ngradients are expected. Such observations have been difficult to make using\nother higher redshift samples because even at redshifts z~0.1 the angular to\nphysical scale is similar to the resolution provided by ground based seeing.\nOur integral field spectroscopy has enabled us to make the first robust\ndetections of Balmer line gradients in the centres of E+A galaxies. Six out of\nour sample of seven, and all the galaxies with regular morphologies, are\nobserved to have compact and centrally-concentrated Balmer line absorption.\nThis is evidence for compact young cores and stellar population gradients which\nare predicted from models of mergers and tidal interactions which funnel gas\ninto the galaxy core. Given the generally isolated nature of our sample this\nargues for the galaxies being seen in the late stage of a merger where the\nprogenitors have already coalesced.", "category": "astro-ph_CO" }, { "text": "There is No Missing Satellites Problem: A critical challenge to the cold dark matter (CDM) paradigm is that there are\nfewer satellites observed around the Milky Way than found in simulations of\ndark matter substructure. We show that there is a match between the observed\nsatellite counts corrected by the detection efficiency of the Sloan Digital Sky\nSurvey (for luminosities $L \\gtrsim$ 340 L$_\\odot$) and the number of luminous\nsatellites predicted by CDM, assuming an empirical relation between stellar\nmass and halo mass. The \"missing satellites problem\", cast in terms of number\ncounts, is thus solved. We also show that warm dark matter models with a\nthermal relic mass smaller than 4 keV are in tension with satellite counts,\nputting pressure on the sterile neutrino interpretation of recent X-ray\nobservations. Importantly, the total number of Milky Way satellites depends\nsensitively on the spatial distribution of satellites, possibly leading to a\n\"too many satellites\" problem. Measurements of completely dark halos below\n$10^8$ M$_\\odot$, achievable with substructure lensing and stellar stream\nperturbations, are the next frontier for tests of CDM.", "category": "astro-ph_CO" }, { "text": "Cosmology before noon with multiple galaxy populations: Near-future facilities observing the high-redshift universe ($20.3. Third, we find that the star\nformation is most efficient in dark matter halos with Mh~5x10^11 Msun, with\nhints of an increase of this mass with redshift. Fourth, we find that SFR/Mh\nincreases by a factor ~15 between z = 0 and z = 2.3. Finally we find that the\nSFR density is dominated by halo masses close to ~7x10^11 Msun at all redshift,\nwith a rapid decrease at lower and higher halo masses. Despite its simplicity,\nour novel use of IR observations unveils some characteristic mass-scales\ngoverning star formation at high redshift.", "category": "astro-ph_CO" }, { "text": "Cyclic Cosmology from the Little Rip: We revisit a cyclic cosmology scenario proposed in 2007 to examine whether\nits hypotheses can be sustained if the underlying big rip evolution, which was\nassumed there, is replaced by the recently proposed little rip. We show that\nthe separation into causal patches at turnaround is generally valid for a\nlittle rip, and therefore conclude that the little rip is equally as suitable a\nbasis for cyclicity as is the big rip.", "category": "astro-ph_CO" }, { "text": "Redshift drift in varying speed of light cosmology: We derive a redshift drift formula within the framework of varying speed of\nlight (VSL) theory using the specific ansatz for the variability of $c(t) = c_0\na^n(t)$. We show that negative values of the parameter $n$, which correspond to\ndiminishing value of the speed of light during the evolution of the universe,\neffectively rescales dust matter to become little negative pressure matter, and\nthe cosmological constant to became phantom. Positive values of $n$ (growing\n$c(t)$) make VSL model to become more like Cold Dark Matter (CDM) model.\nObservationally, there is a distinction between the VSL model and the\n$\\Lambda$CDM model for the admissible values of the parameter $n \\sim -\n10^{-5}$, though it will be rather difficult to detect by planned extremely\nlarge telescopes (E-ELT, TMT, GMT) within their accuracy.", "category": "astro-ph_CO" }, { "text": "Revealing the Dark Matter Halo with Axion Direct Detection: The next generation of axion direct detection experiments may rule out or\nconfirm axions as the dominant source of dark matter. We develop a general\nlikelihood-based framework for studying the time-series data at such\nexperiments, with a focus on the role of dark-matter astrophysics, to search\nfor signatures of the QCD axion or axion like particles. We illustrate how in\nthe event of a detection the likelihood framework may be used to extract\nmeasures of the local dark matter phase-space distribution, accounting for\neffects such as annual modulation and gravitational focusing, which is the\nperturbation to the dark matter phase-space distribution by the gravitational\nfield of the Sun. Moreover, we show how potential dark matter substructure,\nsuch as cold dark matter streams or a thick dark disk, could impact the signal.\nFor example, we find that when the bulk dark matter halo is detected at\n5$\\sigma$ global significance, the unique time-dependent features imprinted by\nthe dark matter component of the Sagittarius stream, even if only a few percent\nof the local dark matter density, may be detectable at $\\sim$2$\\sigma$\nsignificance. A co-rotating dark disk, with lag speed $\\sim$50 km$/$s, that is\n$\\sim$20$\\%$ of the local DM density could dominate the signal, while colder\nbut as-of-yet unknown substructure may be even more important. Our likelihood\nformalism, and the results derived with it, are generally applicable to any\ntime-series based approach to axion direct detection.", "category": "astro-ph_CO" }, { "text": "Type Ia Supernova Colors and Ejecta Velocities: Hierarchical Bayesian\n Regression with Non-Gaussian Distributions: We investigate the statistical dependence of the peak intrinsic colors of\nType Ia supernovae (SN Ia) on their expansion velocities at maximum light,\nmeasured from the Si II 6355 spectral feature. We construct a new hierarchical\nBayesian regression model, accounting for the random effects of intrinsic\nscatter, measurement error, and reddening by host galaxy dust, and implement a\nGibbs sampler and deviance information criteria to estimate the correlation.\nThe method is applied to the apparent colors from BVRI light curves and Si II\nvelocity data for 79 nearby SNe Ia. The apparent color distributions of high\n(HV) and normal velocity (NV) supernovae exhibit significant discrepancies for\nB-V and B-R, but not other colors. Hence, they are likely due to intrinsic\ncolor differences originating in the B-band, rather than dust reddening. The\nmean intrinsic B-V and B-R color differences between HV and NV groups are 0.06\n+/- 0.02 and 0.09 +/- 0.02 mag, respectively. A linear model finds significant\nslopes of -0.021 +/- 0.006 and -0.030 +/- 0.009 mag/(1000 km/s) for intrinsic\nB-V and B-R colors versus velocity, respectively. Since the ejecta velocity\ndistribution is skewed towards high velocities, these effects imply\nnon-Gaussian intrinsic color distributions with skewness up to +0.3. Accounting\nfor the intrinsic color-velocity correlation results in corrections to A_V\nextinction estimates as large as -0.12 mag for HV SNe Ia and +0.06 mag for NV\nevents. Velocity measurements from SN Ia spectra have potential to diminish\nsystematic errors from the confounding of intrinsic colors and dust reddening\naffecting supernova distances.", "category": "astro-ph_CO" }, { "text": "Detailed Calculation of Primordial Black Hole Formation During\n First-Order Cosmological Phase Transitions: We recently presented a new mechanism for primordial black hole formation\nduring a first-order phase transition in the early Universe, which relies on\nthe build-up of particles which are predominantly reflected from the advancing\nbubble wall. In this companion paper we provide details of the supporting\nnumerical calculations. After describing the general mechanism, we discuss the\ncriteria that need to be satisfied for a black hole to form. We then set out\nthe Boltzmann equation that describes the evolution of the relevant phase space\ndistribution function, carefully describing our treatment of the Liouville\noperator and the collision term. Finally, we show that black holes will form\nfor a wide range of parameters.", "category": "astro-ph_CO" }, { "text": "The Data Release of the Sloan Digital Sky Survey-II Supernova Survey: This paper describes the data release of the Sloan Digital Sky Survey-II\n(SDSS-II) Supernova Survey conducted between 2005 and 2007. Light curves,\nspectra, classifications, and ancillary data are presented for 10,258 variable\nand transient sources discovered through repeat ugriz imaging of SDSS Stripe\n82, a 300 deg2 area along the celestial equator. This data release is comprised\nof all transient sources brighter than r~22.5 mag with no history of\nvariability prior to 2004. Dedicated spectroscopic observations were performed\non a subset of 889 transients, as well as spectra for thousands of transient\nhost galaxies using the SDSS-III BOSS spectrographs. Photometric\nclassifications are provided for the candidates with good multi-color light\ncurves that were not observed spectroscopically. From these observations, 4607\ntransients are either spectroscopically confirmed, or likely to be, supernovae,\nmaking this the largest sample of supernova candidates ever compiled. We\npresent a new method for SN host-galaxy identification and derive host-galaxy\nproperties including stellar masses, star-formation rates, and the average\nstellar population ages from our SDSS multi-band photometry. We derive SALT2\ndistance moduli for a total of 1443 SN Ia with spectroscopic redshifts as well\nas photometric redshifts for a further 677 purely-photometric SN Ia candidates.\nUsing the spectroscopically confirmed subset of the three-year SDSS-II SN Ia\nsample and assuming a flat Lambda-CDM cosmology, we determine Omega_M = 0.315\n+/- 0.093 (statistical error only) and detect a non-zero cosmological constant\nat 5.7 sigmas.", "category": "astro-ph_CO" }, { "text": "Imprints of Oscillatory Bispectra on Galaxy Clustering: Long-short mode coupling during inflation, encoded in the squeezed bispectrum\nof curvature perturbations, induces a dependence of the local, small-scale\npower spectrum on long-wavelength perturbations, leading to a scale-dependent\nhalo bias. While this scale dependence is absent in the large-scale limit for\nsingle-field inflation models that satisfy the consistency relation, certain\nmodels such as resonant non-Gaussianity show a peculiar behavior on\nintermediate scales. We reconsider the predictions for the halo bias in this\nmodel by working in Conformal Fermi Coordinates, which isolate the physical\neffects of long-wavelength perturbations on short-scale physics. We find that\nthe bias oscillates with scale with an envelope similar to that of equilateral\nnon-Gaussianity. Moreover, the bias shows a peculiar modulation with the halo\nmass. Unfortunately, we find that upcoming surveys will be unable to detect the\nsignal because of its very small amplitude. We also discuss non-Gaussianity due\nto interactions between the inflaton and massive fields: our results for the\nbias agree with those in the literature.", "category": "astro-ph_CO" }, { "text": "Improved Modeling of the Kinematic Sunyaev-Zel'dovich Projected-Fields\n signal and its Cosmological Dependence: Over the past decade, the kinematic Sunyaev-Zel'dovich (kSZ) effect has\nemerged as an observational probe of the distribution of baryons and velocity\nfields in the late Universe. Of the many ways to detect the kSZ, the\n'projected-fields kSZ estimator' has the promising feature of not being limited\nto galaxy samples with accurate redshifts. The current theoretical modeling of\nthis estimator involves an approximate treatment only applicable at small\nscales. As the measurement fidelity rapidly improves, we find it necessary to\nmove beyond the original treatment and hence derive an improved theoretical\nmodel for this estimator without these previous approximations. We show that\nthe differences between the predicted signal from the two models are\nscale-dependent and will be significant for future measurements from the Simons\nObservatory and CMB-S4 in combination with galaxy data from WISE or the Rubin\nObservatory, which have high forecasted signal-to-noise ratios ($>100$). Thus,\nadopting our improved model in future analyses will be important to avoid\nbiases. Equipped with our model, we explore the cosmological dependence of this\nkSZ signal for future measurements. With a Planck prior, residual uncertainty\non $\\Lambda$CDM parameters leads to $\\sim7\\%$ marginalized uncertainties on the\nsignal amplitude, compared to a sub-percent level forecasted with a fixed\ncosmology. To illustrate the potential of this kSZ estimator as a cosmological\nprobe, we forecast initial constraints on $\\Lambda$CDM parameters and the sum\nof neutrino masses, paving the way for jointly fitting both baryonic\nastrophysics and cosmology in future analyses.", "category": "astro-ph_CO" }, { "text": "Velocity-Density Correlations from the cosmicflows-3 Distance Catalog\n and the 2MASS Redshift Survey: The peculiar velocity of a mass tracer is on average aligned with the dipole\nmodulation of the surrounding mass density field. We present a first\nmeasurement of the correlation between radial peculiar velocities of objects in\nthe cosmicflows-3 catalog and the dipole moment of the 2MRS galaxy distribution\nin concentric spherical shells centered on these objects. Limiting the analysis\nto cosmicflows-3 objects with distances of $100 \\rm Mpc h^{-1}$, the\ncorrelation function is detected at a confidence level $> 4\\sigma$. The\nmeasurement is found consistent with the standard $\\Lambda$CDM model at $<\n1.7\\sigma$ level. We formally derive the constraints\n$0.32<\\Omega^{0.55}\\sigma_8<0.48$ ($68\\% $ confidence level) or equivalently\n$0.34<\\Omega^{0.55}/b<0.52$, where $b$ is the galaxy bias factor. Deeper and\nimproved peculiar velocity catalogs will substantially reduce the\nuncertainties, allowing tighter constraints from this type of correlations.", "category": "astro-ph_CO" }, { "text": "Alleviating the $H_0$ and $\u03c3_8$ anomalies with a decaying dark\n matter model: The Hubble tension between the $\\Lambda$CDM-model-dependent prediction of the\ncurrent expansion rate $H_0$ using Planck data and direct, model-independent\nmeasurements in the local universe from the SH0ES collaboration disagree at\n$>3.5\\sigma$. Moreover, there exists a milder $\\sim 2\\sigma$ tension between\nsimilar predictions for the amplitude $S_8$ of matter fluctuations and its\nmeasurement in the local universe. As explanations relying on unresolved\nsystematics have not been found, theorists have been exploring explanations for\nthese anomalies that modify the cosmological model, altering\nearly-universe-based predictions for these parameters. However, new\ncosmological models that attempt to resolve one tension often worsen the other.\nIn this paper, we investigate a decaying dark matter (DDM) model as a solution\nto both tensions simultaneously. Here, a fraction of dark matter density decays\ninto dark radiation. The decay rate $\\Gamma$ is proportional to the Hubble rate\n$H$ through the constant $\\alpha_{\\rm dr}$, the only additional parameter of\nthis model. Then, this model deviates most from $\\Lambda$CDM in the early\nuniverse, with $\\alpha_{\\rm dr}$ being positively correlated with $H_0$ and\nnegatively with $S_8$. Hence, increasing $\\alpha_{\\rm dr}$ (and allowing dark\nmatter to decay in this way) can then diminish both tensions simultaneously.\nWhen only considering Planck CMB data and the local SH0ES prior on $H_0$, $\\sim\n1$\\% dark matter decays, decreasing the $S_8$ tension to $0.3\\sigma$ and\nincreasing the best-fit $H_0$ by $1.6$ km/s/Mpc. However, the addition of\nintermediate-redshift data (the JLA supernova dataset and baryon acoustic\noscillation data) weakens the effectiveness of this model. Only $\\sim 0.5$\\% of\nthe dark matter decays bringing the $S_8$ tension back up to $\\sim 1.5 \\sigma$\nand the increase in the best-fit $H_0$ down to $0.4$ km/s/Mpc.", "category": "astro-ph_CO" }, { "text": "The impact of the supersonic baryon-dark matter velocity difference on\n the z~20 21cm background: Recently, Tseliakhovich and Hirata (2010) showed that during the cosmic Dark\nAges the baryons were typically moving supersonically with respect to the dark\nmatter with a spatially variable Mach number. Such supersonic motion may source\nshocks that heat the Universe. This motion may also suppress star formation in\nthe first halos. Even a small amount of coupling of the 21cm signal to this\nmotion has the potential to vastly enhance the 21cm brightness temperature\nfluctuations at 156$ for Pop\nIII.2 and $N < 0.08$ per year integrated over at $z>10$ for Pop III.1 with\nEXIST, and $N < 0.2$ for Pop III.2 GRBs per year integrated over at $z > 6$\nwith \\textit{Swift}.", "category": "astro-ph_CO" }, { "text": "Measuring the lensing potential with tomographic galaxy number counts: We investigate how the lensing potential can be measured tomographically with\nfuture galaxy surveys using their number counts. Such a measurement is an\nindependent test of the standard $\\Lambda$CDM framework and can be used to\ndiscern modified theories of gravity. We perform a Fisher matrix forecast based\non galaxy angular-redshift power spectra, assuming specifications consistent\nwith future photometric Euclid-like surveys and spectroscopic SKA-like surveys.\nFor the Euclid-like survey we derive a fitting formula for the magnification\nbias. Our analysis suggests that the cross correlation between different\nredshift bins is very sensitive to the lensing potential such that the survey\ncan measure the amplitude of the lensing potential at the same level of\nprecision as other standard $\\Lambda$CDM cosmological parameters.", "category": "astro-ph_CO" }, { "text": "The Extragalactic Distance Database: A database can be accessed on the web at http://edd.ifa.hawaii.edu that was\ndeveloped to promote access to information related to galaxy distances. The\ndatabase has three functional components. First, tables from many literature\nsources have been gathered and enhanced with links through a distinct galaxy\nnaming convention. Second, comparisons of results both at the levels of\nparameters and of techniques have begun and are continuing, leading to\nincreasing homogeneity and consistency of distance measurements. Third, new\nmaterial are presented arising from ongoing observational programs at the\nUniversity of Hawaii 2.2m telescope, radio telescopes at Green Bank, Arecibo,\nand Parkes and with Hubble Space Telescope. This new observational material is\nmade available in tandem with related material drawn from archives and passed\nthrough common analysis pipelines.", "category": "astro-ph_CO" }, { "text": "Integral field spectroscopy with SINFONI of VVDS galaxies. I. Galaxy\n dynamics and mass assembly at 1.2 < z < 1.6: Context. Identifying the main processes of galaxy assembly at high redshifts\nis still a major issue to understand galaxy formation and evolution at early\nepochs in the history of the Universe. Aims. This work aims to provide a first\ninsight into the dynamics and mass assembly of galaxies at redshifts 1.210^11Msun subject to at least one major merger over a 3\nGyr period as well as for continuous accretion feeding strong star formation.\nConclusions. These results point towards a galaxy formation and assembly\nscenario which involves several processes, possibly acting in parallel, with\nmajor mergers and continuous gas accretion playing a major role. Well\ncontrolled samples representative of the bulk of the galaxy population at this\nkey cosmic time are necessary to make further progress.", "category": "astro-ph_CO" }, { "text": "Cosmological Limits on Hidden Sector Dark Matter: We explore the model-independent constraints from cosmology on a dark-matter\nparticle with no prominent standard model interactions that interacts and\nthermalizes with other particles in a hidden sector. Without specifying\ndetailed hidden-sector particle physics, we characterize the relevant physics\nby the annihilation cross section, mass, and temperature ratio of the hidden to\nvisible sectors. While encompassing the standard cold WIMP scenario, we do not\nrequire the freeze-out process to be nonrelativistic. Rather, freeze-out may\nalso occur when dark matter particles are semirelativistic or relativistic. We\nsolve the Boltzmann equation to find the conditions that hidden-sector dark\nmatter accounts for the observed dark-matter density, satisfies the\nTremaine-Gunn bound on dark-matter phase space density, and has a\nfree-streaming length consistent with cosmological constraints on the matter\npower spectrum. We show that for masses <1.5 keV no region of parameter space\nsatisfies all these constraints. This is a gravitationally-mediated lower bound\non the dark-matter mass for any model in which the primary component of dark\nmatter once had efficient interactions -- even if it has never been in\nequilibrium with the standard model.", "category": "astro-ph_CO" }, { "text": "Abell 2744 may be a supercluster aligned along the sightline: To explain the unusual richness and compactness of the Abell 2744, we propose\na hypothesis that it may be a rich supercluster aligned along the sightline,\nand present a supporting evidence obtained numerically from the MultiDark\nPlanck 2 simulations with a linear box size of $1\\,h^{-1}$Gpc. Applying the\nfriends-of-friends (FoF) algorithm with a linkage length of $0.33$ to a sample\nof the cluster-size halos from the simulations, we identify the superclusters\nand investigate how many superclusters have filamentary branches that would\nappear to be similar to the Abell 2744 if the filamentary axis is aligned with\nthe sightline. Generating randomly a unit vector as a sightline at the position\nof the core member of each supercluster and projecting the positions of the\nmembers onto the plane perpendicular to the direction of the sightline, we\nmeasure two dimensional distances ($R_{2d}$) of the member halos from the core\nfor each supercluster. Defining a Abell 2744-like spuercluster as the one\nhaving a filamentary branch composed of eight or more members with $R_{2d}\\le\n1\\,$Mpc and masses comparable to those of the observed Abell 2744\nsubstructures, we find one Abell 2744-like supercluster at $z=0.3$ and two at\n$z=0$. Repeating the same analysis but with the data from the Big MultiDark\nPlanck simulations performed on a larger box of linear size of\n$2.5\\,h^{-1}$Mpc, we find that the number of the Abell 2744-like superclusters\nat $z=0$ increases up to eighteen, among which three are found more massive\nthan $5\\times 10^{15}\\,M_{\\odot}$.", "category": "astro-ph_CO" }, { "text": "The Herschel-SPIRE Legacy Survey (HSLS): the scientific goals of a\n shallow and wide submillimeter imaging survey with SPIRE: A large sub-mm survey with Herschel will enable many exciting science\nopportunities, especially in an era of wide-field optical and radio surveys and\nhigh resolution cosmic microwave background experiments. The Herschel-SPIRE\nLegacy Survey (HSLS), will lead to imaging data over 4000 sq. degrees at 250,\n350, and 500 micron. Major Goals of HSLS are: (a) produce a catalog of 2.5 to 3\nmillion galaxies down to 26, 27 and 33 mJy (50% completeness; 5 sigma confusion\nnoise) at 250, 350 and 500 micron, respectively, in the southern hemisphere\n(3000 sq. degrees) and in an equatorial strip (1000 sq. degrees), areas which\nhave extensive multi-wavelength coverage and are easily accessible from ALMA.\nTwo thirds of the of the sources are expected to be at z > 1, one third at z >\n2 and about a 1000 at z > 5. (b) Remove point source confusion in secondary\nanisotropy studies with Planck and ground-based CMB data. (c) Find at least\n1200 strongly lensed bright sub-mm sources leading to a 2% test of general\nrelativity. (d) Identify 200 proto-cluster regions at z of 2 and perform an\nunbiased study of the environmental dependence of star formation. (e) Perform\nan unbiased survey for star formation and dust at high Galactic latitude and\nmake a census of debris disks and dust around AGB stars and white dwarfs.", "category": "astro-ph_CO" }, { "text": "Constraints on non-resonant photon-axion conversion from the Planck\n satellite data: The non-resonant conversion of Cosmic Microwave Background (CMB) photons into\nscalar as well as light pseudoscalar particles such as axion-like particles\n(ALPs) in the presence of turbulent magnetic fields can cause a unique,\nspatially fluctuating spectral distortion in the CMB. We use the publicly\navailable Planck temperature maps for the frequency channels (70-545 GHz) to\nobtain the first ALP distortion map using $45\\%$ clean part of the sky. The\n$95^{th}$ percentile upper limit on the RMS fluctuation of ALP distortions from\nthe cleanest part of the CMB sky at $15$ arcmin angular resolution is $18.5\n\\times 10^{-6}$. The RMS fluctuation in the distortion map is also consistent\nwith different combinations of frequency channels and sky-fractions.", "category": "astro-ph_CO" }, { "text": "Astrophysical Probes of Fundamental Physics: The dramatic confrontation between new observations and theories of the early\nand recent universe makes cosmology one of the most rapidly advancing fields in\nthe physical sciences. The universe is a unique laboratory in which to probe\nfundamental physics, the rationale being to start from fundamental physics\ninspired models and explore their consequences in sufficient quantitative\ndetail to be able to identify key astrophysical and cosmological tests of the\nunderlying theory (or developing new tests when appropriate). An unprecedented\nnumber of such tests will be possible in the coming years, by exploiting the\never improving observational data. In this spirit I will highlight some open\nissues in cosmology and particle physics and provide some motivation for this\nsymposium.", "category": "astro-ph_CO" }, { "text": "On the Lyth bound and single field slow-roll inflation: We take a pragmatic, model independent approach to single field slow-roll\ninflation by imposing conditions to the slow-roll parameter $\\epsilon$ and its\nderivative $\\epsilon^{\\prime }.$ To accommodate the recent (large) values of\n$r$ reported by the BICEP2 collaboration we advocate for a decreasing\n$\\epsilon$ during most part of inflation. However because at\n$\\phi_{\\mathrm{H}}$, at which the perturbations are produced, some $50$ $-$\n$60$ e-folds before the end of inflation, $\\epsilon$ is increasing we thus\nrequire that $\\epsilon$ develops a maximum for $\\phi > \\phi_{\\mathrm{H}}$ and\nthen decrease to small values where most e-folds are produced. The end of\ninflation might occur trough a hybrid field and a small $\\Delta\\phi$ is\nobtained with a sufficiently thin $\\epsilon$ which, however, should not\nconflict with the curvature of the potential measured by the second slow-roll\nparameter $\\eta$. The conclusion is that under these circumstances $\\Delta\\phi$\nand the spectral index $n_{\\mathrm{s}}$ are restricted to narrow windows of\nvalues.", "category": "astro-ph_CO" }, { "text": "Structures of Local Galaxies Compared to High Redshift Star-forming\n Galaxies: The rest-frame far-ultraviolet (FUV) morphologies of 8 nearby interacting and\nstarburst galaxies (Arp 269, M 82, Mrk 8, NGC 520, NGC 1068, NGC 3079, NGC\n3310, NGC 7673) are compared with 54 galaxies at z ~ 1.5 and 46 galaxies at z ~\n4 observed in the GOODS-ACS field. The nearby sample is artificially redshifted\nto z ~ 1.5 and 4. We compare the simulated galaxy morphologies to real z ~ 1.5\nand 4 UV-bright galaxy morphologies. We calculate the Gini coefficient (G), the\nsecond-order moment of the brightest 20% of the galaxy's flux (M_20), and the\nSersic index (n). We explore the use of nonparametric methods with 2D profile\nfitting and find the combination of M_20 with n an efficient method to classify\ngalaxies as having merger, exponential disk, or bulge-like morphologies. When\nclassified according to G and M_20, 20/30% of real/simulated galaxies at z ~\n1.5 and 37/12% at z ~ 4 have bulge-like morphologies. The rest have merger-like\nor intermediate distributions. Alternatively, when classified according to the\nSersic index, 70% of the z ~ 1.5 and z ~ 4 real galaxies are exponential disks\nor bulge-like with n > 0.8, and ~30% of the real galaxies are classified as\nmergers. The artificially redshifted galaxies have n values with ~35% bulge or\nexponential at z ~ 1.5 and 4. Therefore, ~20-30% of Lyman-break galaxies (LBGs)\nhave structures similar to local starburst mergers, and may be driven by\nsimilar processes. We assume merger-like or clumpy star-forming galaxies in the\nGOODS field have morphological structure with values n < 0.8 and M_20 > -1.7.\nWe conclude that Mrk 8, NGC 3079, and NGC 7673 have structures similar to those\nof merger-like and clumpy star-forming galaxies observed at z ~ 1.5 and 4.", "category": "astro-ph_CO" }, { "text": "The Power Spectra of Polarized, Dusty Filaments: We develop an analytic model for the power spectra of polarized filamentary\nstructures as a way to study the Galactic polarization foreground to the Cosmic\nMicrowave Background. Our approach is akin to the cosmological halo-model\nframework, and reproduces the main features of the Planck 353 GHz power\nspectra. We model the foreground as randomly-oriented, three-dimensional,\nspheroidal filaments, accounting for their projection onto the sky. The main\ntunable parameters are the distribution of filament sizes, the filament\nphysical aspect ratio, and the dispersion of the filament axis around the local\nmagnetic field direction. The abundance and properties of filaments as a\nfunction of size determine the slopes of the foreground power spectra, as we\nshow via scaling arguments. The filament aspect ratio determines the ratio of\n$B$-mode power to $E$-mode power, and specifically reproduces the\nPlanck-observed dust ratio of one-half when the short axis is roughly\none-fourth the length of the long axis. Filament misalignment to the local\nmagnetic field determines the $TE$ cross-correlation, and to reproduce Planck\nmeasurements, we need a (three-dimensional) misalignment angle with a root mean\nsquared dispersion of about 50 degrees. These parameters are not sensitive to\nthe particular filament density profile. By artificially skewing the\ndistribution of the misalignment angle, this model can reproduce the\nPlanck-observed (and parity-violating) $TB$ correlation. The skewing of the\nmisalignment angle necessary to explain $TB$ will cause a yet-unobserved,\npositive $EB$ dust correlation, a possible target for future experiments.", "category": "astro-ph_CO" }, { "text": "Structure formation with suppressed small-scale perturbations: All commonly considered dark matter scenarios are based on hypothetical\nparticles with small but non-zero thermal velocities and tiny interaction\ncross-sections. A generic consequence of these attributes is the suppression of\nsmall-scale matter perturbations either due to free-streaming or due to\ninteractions with the primordial plasma. The suppression scale can vary over\nmany orders of magnitude depending on particle candidate and production\nmechanism in the early Universe. While nonlinear structure formation has been\nexplored in great detail well above the suppression scale, the range around\nsuppressed perturbations is still poorly understood. In this paper we study\nstructure formation in the regime of suppressed perturbations using both\nanalytical techniques and numerical simulations. We develop simple and\ntheoretically motivated recipes for the halo mass function, the expected number\nof satellites, and the halo concentrations, which are designed to work for\npower spectra with suppression at arbitrary scale and of arbitrary shape. As\ncase studies, we explore warm and mixed dark matter scenarios where effects are\nmost distinctive. Additionally, we examine the standard dark matter scenario\nbased on weakly interacting massive particles (WIMP) and compare it to pure\ncold dark matter with zero primordial temperature. We find that our\nanalytically motivated recipes are in good agreement with simulations for all\ninvestigated dark matter scenarios, and we therefore conclude that they can be\nused for generic cases with arbitrarily suppressed small-scale perturbations.", "category": "astro-ph_CO" }, { "text": "Neutral hydrogen in galaxy clusters: impact of AGN feedback and\n implications for intensity mapping: By means of zoom-in hydrodynamic simulations we quantify the amount of\nneutral hydrogen (HI) hosted by groups and clusters of galaxies. Our\nsimulations, which are based on an improved formulation of smoothed particle\nhydrodynamics (SPH), include radiative cooling, star formation, metal\nenrichment and supernova feedback, and can be split in two different groups,\ndepending on whether feedback from active galactic nuclei (AGN) is turned on or\noff. Simulations are analyzed to account for HI self-shielding and the presence\nof molecular hydrogen. We find that the mass in neutral hydrogen of dark matter\nhalos monotonically increases with the halo mass and can be well described by a\npower-law of the form $M_{\\rm HI}(M,z)\\propto M^{3/4}$. Our results point out\nthat AGN feedback reduces both the total halo mass and its HI mass, although it\nis more efficient in removing HI. We conclude that AGN feedback reduces the\nneutral hydrogen mass of a given halo by $\\sim50\\%$, with a weak dependence on\nhalo mass and redshift. The spatial distribution of neutral hydrogen within\nhalos is also affected by AGN feedback, whose effect is to decrease the\nfraction of HI that resides in the halo inner regions. By extrapolating our\nresults to halos not resolved in our simulations we derive astrophysical\nimplications from the measurements of $\\Omega_{\\rm HI}(z)$: halos with circular\nvelocities larger than $\\sim25~{\\rm km/s}$ are needed to host HI in order to\nreproduce observations. We find that only the model with AGN feedback is\ncapable of reproducing the value of $\\Omega_{\\rm HI}b_{\\rm HI}$ derived from\navailable 21cm intensity mapping observations.", "category": "astro-ph_CO" }, { "text": "Updated constraint on a primordial magnetic field during big bang\n nucleosynthesis and a formulation of field effects: A new upper limit on the amplitude of primordial magnetic field (PMF) is\nderived by a comparison between a calculation of elemental abundances in big\nbang nucleosynthesis (BBN) model and the latest observational constraints on\nthe abundances. Updated nuclear reaction rates are adopted in the calculation.\nEffects of PMF on the abundances are consistently taken into account in the\nnumerical calculation with the precise formulation of changes in physical\nvariables. We find that abundances of 3He and 6Li increase while that of 7Li\ndecreases when the PMF amplitude increases, in the case of the baryon-to-photon\nratio determined from the measurement of cosmic microwave background radiation.\nWe derive a constraint on the present amplitude of PMF, i.e., B(0)<1.5 micro G\n[corresponding to the amplitude less than 2.0x10^{11} G at BBN temperature of\nT=10^9 K] based on the rigorous calculation.", "category": "astro-ph_CO" }, { "text": "Forecast and analysis of the cosmological redshift drift: The cosmological redshift drift could lead to the next step in high-precision\ncosmic geometric observations, becoming a direct and irrefutable test for\ncosmic acceleration. In order to test the viability and possible properties of\nthis effect, also called Sandage-Loeb (SL) test, we generate a model\nindependent mock data set so as to compare its constraining power with that of\nthe future mock data sets of Type Ia Supernovae (SNe) and Baryon Acoustic\nOscillations (BAO). The performance of those data sets is analyzed by testing\nseveral cosmological models with the Markov chain Monte Carlo (MCMC) method,\nboth independently and combining all data sets. Final results show that, in\ngeneral, SL data sets allow for remarkable constraints on the matter density\nparameter today $\\Omega_m$ on every tested model, showing also a great\ncomplementarity with SNe and BAO data regarding dark energy (DE) parameters.", "category": "astro-ph_CO" }, { "text": "On the Bispectra of Very Massive Tracers in the Effective Field Theory\n of Large-Scale Structure: The Effective Field Theory of Large-Scale Structure (EFTofLSS) provides a\nconsistent perturbative framework for describing the statistical distribution\nof cosmological large-scale structure. In a previous EFTofLSS calculation that\ninvolved the one-loop power spectra and tree-level bispectra, it was shown that\nthe $k$-reach of the prediction for biased tracers is comparable for all\ninvestigated masses if suitable higher-derivative biases, which are less\nsuppressed for more massive tracers, are added. However, it is possible that\nthe non-linear biases grow faster with tracer mass than the linear bias,\nimplying that loop contributions could be the leading correction to the\nbispectra. To check this, we include the one-loop contributions in a fit to\nnumerical data in the limit of strongly enhanced higher-order biases. We show\nthat the resulting one-loop power spectra and higher-derivative plus leading\none-loop bispectra fit the two- and three-point functions respectively up to\n$k\\simeq 0.19\\ h\\ \\rm{Mpc}^{-1}$ and $k\\simeq 0.14\\ h\\ \\rm{Mpc}^{-1}$ at the\npercent level. We find that the higher-order bias coefficients are not strongly\nenhanced, and we argue that the gain in perturbative reach due to the leading\none-loop contributions to the bispectra is relatively small. Thus, we conclude\nthat higher-derivative biases provide the leading correction to the bispectra\nfor tracers of a very wide range of masses.", "category": "astro-ph_CO" }, { "text": "The Structure of HE 1104-1805 from Infrared to X-Ray: The gravitationally lensed quasar HE 1104-1805 has been observed at a variety\nof wavelengths ranging from the mid-infrared to X-ray for nearly 20 years. We\ncombine flux ratios from the literature, including recent Chandra data, with\nnew observations from the SMARTS telescope and HST, and use them to investigate\nthe spatial structure of the central regions using a Bayesian Monte Carlo\nanalysis of the microlensing variability. The wide wavelength coverage allows\nus to constrain not only the accretion disk half-light radius r_1/2, but the\npower-law slope \\xi\\ of the size-wavelength relation r_1/2 ~ \\lambda^\\xi. With\na logarithmic prior on the source size, the (observed-frame) R-band half-light\nradius log(r_1/2/cm) is 16.0+0.3-0.4, and the slope \\xi\\ is 1.0+0.30-0.56. We\nput upper limits on the source size in soft (0.4-1.2 keV) and hard (1.2-8 keV)\nX-ray bands, finding 95% upper limits on log (r_1/2/cm) of 15.33 in both bands.\nA linear prior yields somewhat larger sizes, particularly in the X-ray bands.\nFor comparison, the gravitational radius, using a black hole mass estimated\nusing the H\\beta\\ line, is log(r_g/cm) = 13.94. We find that the accretion disk\nis probably close to face-on, with cos i = 1.0 being four times more likely\nthan cos i = 0.5. We also find probability distributions for the mean mass of\nthe stars in the foreground lensing galaxy, the direction of the transverse\npeculiar velocity of the lens, and the position angle of the projected\naccretion disk's major axis (if not face-on).", "category": "astro-ph_CO" }, { "text": "Magnetic Fields of Agns and Standard Accretion Disk Model: Testing by\n Optical Polarimetry: We have developed the method that allows us to estimate the magnetic field\nstrength at the horizon of a supermassive black hole (SMBH) through the\nobserved polarization of optical emission of the accreting disk surrounding\nSMBH. The known asymptotic formulae for the Stokes parameters of outgoing\nradiation are azimuthal averaged, which corresponds to an observation of the\ndisk as a whole. We consider two models of the embedding 3D-magnetic field, the\nregular field, and the regular field with an additional chaotic (turbulent)\ncomponent. It is shown that the second model is preferable for estimating the\nmagnetic field in NGC 4258. For estimations we used the standard accretion disk\nmodel assuming that the same power-law dependence of the magnetic field follows\nfrom the range of the optical emission down to the horizon. The observed\noptical polarization from NGC 4258 allowed us to find the values 10^3 - 10^4\nGauss at the horizon, depending on the particular choice of the model\nparameters. We also discuss the wavelength dependencies of the light\npolarization, and possibly applying them for a more realistic choice of\naccretion disk parameters.", "category": "astro-ph_CO" }, { "text": "Galaxy Bias and $\u03c3_8$ from Counts in Cells from the SDSS Main\n Sample: The counts-in-cells (CIC) galaxy probability distribution depends on both the\ndark matter clustering amplitude $\\sigma_8$ and the galaxy bias $b$. We present\na theory for the CIC distribution based on a previous prescription of the\nunderlying dark matter distribution and a linear volume transformation to\nredshift space. We show that, unlike the power spectrum, the CIC distribution\nbreaks the degeneracy between $\\sigma_8$ and $b$ on scales large enough that\nboth bias and redshift distortions are still linear; thus we obtain a\nsimultaneous fit for both parameters. We first validate the technique on the\nMillennium Simulation and then apply it to the SDSS Main Galaxy Sample. We find\n$\\sigma_8 = 0.94^{+.11}_{-.10}$ and $b = 1.36^{+.14}_{-.11}$, consistent with\nprevious complementary results from redshift distortions and from Planck.", "category": "astro-ph_CO" }, { "text": "Discovery of Hydrogen Fluoride in the Cloverleaf Quasar at z = 2.56: We report the first detection of hydrogen fluoride (HF) toward a high\nredshift quasar. Using the Caltech Submillimeter Observatory (CSO) we detect\nthe HF J = 1 - 0 transition in absorption toward the Cloverleaf, a broad\nabsorption line (BAL) quasi-stellar object (QSO) at z=2.56. The detection is\nstatistically significant at the ~ 6 sigma level. We estimate a lower limit of\n4 \\times 1014 cm-2 for the HF column density and using a previous estimate of\nthe hydrogen column density, we obtain a lower limit of 1.7 \\times 10-9 for the\nHF abundance. This value suggests that, assuming a Galactic N(HF)/NH ratio, HF\naccounts for at least ~10% of the fluorine in the gas phase along the line of\nsight to the Cloverleaf quasar. This observation corroborates the prediction\nthat HF should be a good probe of the molecular gas at high redshift.\nMeasurements of the HF abundance as a function of redshift are urgently needed\nto better constrain the fluorine nucleosynthesis mechanism(s).", "category": "astro-ph_CO" }, { "text": "Testing MONDian Dark Matter with Galactic Rotation Curves: MONDian dark matter (MDM) is a new form of dark matter quantum that naturally\naccounts for Milgrom's scaling, usually associated with modified Newtonian\ndynamics (MOND), and theoretically behaves like cold dark matter (CDM) at\ncluster and cosmic scales. In this paper, we provide the first observational\ntest of MDM by fitting rotation curves to a sample of 30 local spiral galaxies\n(z approximately 0.003). For comparison, we also fit the galactic rotation\ncurves using MOND, and CDM. We find that all three models fit the data well.\nThe rotation curves predicted by MDM and MOND are virtually indistinguishable\nover the range of observed radii (~1 to 30 kpc). The best-fit MDM and CDM\ndensity profiles are compared. We also compare with MDM the dark matter density\nprofiles arising from MOND if Milgrom's formula is interpreted as Newtonian\ngravity with an extra source term instead of as a modification of inertia. We\nfind that discrepancies between MDM and MOND will occur near the center of a\ntypical spiral galaxy. In these regions, instead of continuing to rise sharply,\nthe MDM mass density turns over and drops as we approach the center of the\ngalaxy. Our results show that MDM, which restricts the nature of the dark\nmatter quantum by accounting for Milgrom's scaling, accurately reproduces\nobserved rotation curves.", "category": "astro-ph_CO" }, { "text": "Angular Correlation Function from sample covariance with BOSS and eBOSS\n LRG: The Baryon Acoustic Oscillations (BAO) are one of the most used probes to\nunderstand the accelerated expansion of the Universe. Traditional methods rely\non fiducial model information within their statistical analysis, which may be a\nproblem when constraining different families of models. The aim of this work is\nto provide a method that constrains $\\theta_{BAO}$ through a model-independent\nand compare parameter estimation of the angular correlation function polynomial\napproach, using the covariance matrix from the galaxy sample from thin redshift\nbins, with the usual mock sample covariance matrix. We proposed a different\napproach to finding the BAO angular feature revisiting previous work in the\nliterature, we take the bias between the correlation function between the bins\nand the whole sample. We used widths of $\\delta z = 0.002$ separation for all\nsamples as the basis for a sample covariance matrix weighted by the statistical\nimportance of the redshift bin. We propose a different weighting scheme based\nonly on random pair counting. We also propose an alternate shift parameter\nbased only on the data. Each sample belongs to the Sloan Digital Sky Survey\nLuminous Red Galaxies (LRG): BOSS1, BOSS2, and eBOSS, with effective redshift\n$z_{eff}$: 0.35, 0.51, 0.71, respectively, and different numbers of bins with\n50, 100, and 200 respectively. In addition, we correct the angular separation\nfrom the polynomial fit ($\\theta_{fit}$) that encodes the BAO feature with a\nbias function obtained by comparing each bin correlation function with the\ncorrelation function of the whole set. We also tested the same correction\nchoosing the bin at $z_{eff}$ and found that for eBOSS $\\theta_{BAO}$ is in $1\n\\sigma$ agreement with the Planck 18 model. BOSS1 and BOSS2 $\\theta_{BAO}$\nagreed in $1\\sigma$ with the Pantheon+ & S$H_0$ES Flat$\\Lambda$CDM model, in\ntension with Planck 18.", "category": "astro-ph_CO" }, { "text": "Effective Theory of Large-Scale Structure with Primordial\n Non-Gaussianity: We develop the effective theory of large-scale structure for non-Gaussian\ninitial conditions. The effective stress tensor in the dark matter equations of\nmotion contains new operators, which originate from the squeezed limit of the\nprimordial bispectrum. Parameterizing the squeezed limit by a scaling and an\nangular dependence, captures large classes of primordial non-Gaussianity.\nWithin this parameterization, we classify the possible contributions to the\neffective theory. We show explicitly how all terms consistent with the\nsymmetries arise from coarse graining the dark matter equations of motion and\nits initial conditions. We also demonstrate that the system is closed under\nrenormalization and that the basis of correction terms is therefore complete.\nThe relevant corrections to the matter power spectrum and bispectrum are\ncomputed numerically and their relative importance is discussed.", "category": "astro-ph_CO" }, { "text": "Detecting relic gravitational waves in the CMB: Optimal parameters and\n their constraints: The prospect of detecting relic gravitational waves (RGWs), through their\nimprint in the cosmic microwave background radiation, provides an excellent\nopportunity to study the very early Universe. In simplest viable theoretical\nmodels the RGW background is characterized by two parameters, the\ntensor-to-scalar ratio $r$ and the tensor spectral index $n_t$. In this paper,\nwe analyze the potential joint constraints on these two parameters, $r$ and\n$n_t$, using the data from the upcoming cosmic microwave background radiation\nexperiments. Introducing the notion of the best pivot multipole $\\ell_t^*$, we\nfind that at this pivot multipole the parameters $r$ and $n_t$ are\nuncorrelated, and have the smallest variances. We derive the analytical\nformulae for the best pivot multipole number $\\ell_t^*$, and the variances of\nthe parameters $r$ and $n_t$. We verify these analytical calculations using\nnumerical simulation methods, and find agreement to within 20%. The analytical\nresults provides a simple way to estimate the detection ability for the relic\ngravitational waves by the future observations of the cosmic microwave\nbackground radiation.", "category": "astro-ph_CO" }, { "text": "The effect of early radiation in N-body simulations of cosmic structure\n formation: Newtonian N-body simulations have been employed successfully over the past\ndecades for the simulation of the cosmological large-scale structure. Such\nsimulations usually ignore radiation perturbations (photons and massless\nneutrinos) and the impact of general relativity (GR) beyond the background\nexpansion. This approximation can be relaxed and we discuss three different\napproaches that are accurate to leading order in GR. For simulations that start\nat redshift less than about 100 we find that the presence of early radiation\ntypically leads to percent-level effects on the numerical power spectra at\nlarge scales. Our numerical results agree across the three methods, and we\nconclude that all of the three methods are suitable for simulations in a\nstandard cosmology. Two of the methods modify the N-body evolution directly,\nwhile the third method can be applied as a post-processing prescription.", "category": "astro-ph_CO" }, { "text": "Redshift-space distortions with wide angular separations: Redshift-space distortions are generally considered in the plane parallel\nlimit, where the angular separation between the two sources can be neglected.\nGiven that galaxy catalogues now cover large fractions of the sky, it becomes\nnecessary to consider them in a formalism which takes into account the wide\nangle separations. In this article we derive an operational formula for the\nmatter correlators in the Newtonian limit to be used in actual data sets, both\nin configuration and in Fourier spaces without relying on a plane-parallel\napproximation. We then recover the plane-parallel limit not only in\nconfiguration space where the geometry is simpler, but also in Fourier space,\nand we exhibit the first corrections that should be included in large surveys\nas a perturbative expansion over the plane-parallel results. We finally compare\nour results to existing literature, and show explicitly how they are related.", "category": "astro-ph_CO" }, { "text": "Probing Two-Field Open Inflation by Resonant Signals in Correlation\n Functions: We derive oscillatory signals in correlation functions in two-field open\ninflation by means of the in-in formalism; such signatures are caused by\nresonances between oscillations in the tunnelling field and fluctuations in the\ninflaton during the curvature dominated, intermediate and subsequent\ninflationary regime. While amplitudes are model-dependent, we find distinct\noscillations in the power and bi-spectrum that can act as a direct probe of the\ncurvature dominated phase and thus, indirectly, strengthen the claim of the\nstring landscape if they were observed. We comment on the prospects of\ndetecting these tell-tale signs in current experiments, which is challenging,\nbut not impossible.\n At the technical level, we pay special attention to the applicability\nconditions for truncation fluctuations to the light (inflaton) field and derive\nupper limits on the oscillation amplitude of the heavy field. A violation of\nthese bounds requires a multi-field analysis at the perturbed level.", "category": "astro-ph_CO" }, { "text": "Ammonia as a Temperature Tracer in the Ultraluminous Galaxy Merger\n Arp220: (abridged) We present ATCA and GBT observations of ammonia (NH3) toward the\nultraluminous infrared galaxy (ULIRG) merger Arp220. We detect the NH3 (1,1),\n(2,2), (3,3), (4,4), (5,5), and (6,6) inversion lines in absorption against the\nunresolved, (62+/-9)mJy continuum source at 1.2cm. The peak apparent optical\ndepths of the NH3 lines range from ~0.05 to 0.18. The absorption depth of the\nNH3 (1,1) line is significantly shallower than expected based on the depths of\nthe other transitions, which might be caused by contamination from emission by\na hypothetical, cold (<~20K) gas layer with an estimated column density of <~\n2x10^14 cm^-2. The widths of the NH3 absorption lines are ~120-430 km s^-1, in\nagreement with those of other molecular tracers. We cannot confirm the\nextremely large linewidths of up to ~1800km s^-1 previously reported. We\ndetermine a rotational temperature of (124+/-19)K, corresponding to a kinetic\ntemperature of T_kin=(186+/-55)K. NH3 column densities depend on the excitation\ntemperature. For an excitation temperature of 50K, we estimate\n(8.4+/-0.5)x10^16cm^-2. The relation scales linearly for possible higher\nexcitation temperatures. In the context of a model with a molecular ring that\nconnects the two nuclei in Arp220, we estimate the H2 gas density to be\n~f_V^-0.5 x (1-4)x10^3, (f_V: volume filling factor). In addition to NH3, our\nATCA data show an absorption feature adjacent in frequency to the NH3 (3,3)\nline. If we interpret the line to be from the OH ^2Pi_3/2 J=9/2 F=4-4\ntransition, it would have a linewidth, systemic velocity, and apparent optical\ndepth similar to what we detect in the NH3 lines. If this association with OH\nis correct, it marks the first detection of the highly excited (~511K above\nground state) ^2Pi_3/2 J=9/2 F=4-4 OH line in an extragalactic object.", "category": "astro-ph_CO" }, { "text": "Redshift Space Distortion of the 21cm Background from the Epoch of\n Reionization I: Methodology Re-examined: The peculiar velocity of the intergalactic gas responsible for the cosmic\n21cm background from the epoch of reionization and beyond introduces an\nanisotropy in the three-dimensional power spectrum of brightness temperature\nfluctuations. Measurement of this anisotropy by future 21cm surveys is a\npromising tool for separating cosmology from 21cm astrophysics. However,\nprevious attempts to model the signal have often neglected peculiar velocity or\nonly approximated it crudely. This paper re-examines the effects of peculiar\nvelocity on the 21cm signal in detail, improving upon past treatment and\naddressing several issues for the first time. (1) We show that properly\naccounting for finite optical depth eliminates the unphysical divergence of\n21cm brightness temperature in overdense regions of the IGM found by previous\nwork that employed the usual optically-thin approximation. (2) The\napproximation made previously to circumvent the diverging brightness\ntemperature problem by capping velocity gradient can misestimate the power\nspectrum on all scales. (3) The observed power spectrum in redshift-space\nremains finite even in the optically-thin approximation if one properly\naccounts for the redshift-space distortion. However, results that take full\naccount of finite optical depth show that this approximation is only accurate\nin the limit of high spin temperature. (4) The linear theory for redshift-space\ndistortion results in ~30% error in the observationally relevant wavenumber\nrange, at the 50% ionized epoch. (5) We describe and test two numerical schemes\nto calculate the 21cm signal from reionization simulations to incorporate\npeculiar velocity effects in the optically-thin approximation accurately. One\nis particle-based, the other grid-based, and while the former is most accurate,\nwe demonstrate that the latter is computationally more efficient and can\nachieve sufficient accuracy. [Abridged]", "category": "astro-ph_CO" }, { "text": "Is a co-rotating Dark Disk a threat to Dark Matter Directional Detection\n ?: Recent N-Body simulations are in favor of the presence of a co-rotating Dark\nDisk that might contribute significantly (10%-50%) to the local Dark Matter\ndensity. Such substructure could have dramatic effect on directional detection.\nIndeed, in the case of a null lag velocity, one expects an isotropic WIMP\nvelocity distribution arising from the Dark Disk contribution, which might\nweaken the strong angular signature expected in directional detection. For a\nwide range of Dark Disk parameters, we evaluate in this Letter the effect of\nsuch dark component on the discovery potential of upcoming directional\ndetectors. As a conclusion of our study, using only the angular distribution of\nnuclear recoils, we show that Dark Disk models as suggested by recent N-Body\nsimulations will not affect significantly the Dark Matter reach of directional\ndetection, even in extreme configurations.", "category": "astro-ph_CO" }, { "text": "Supernovae in paired galaxies: We investigate the influence of close neighbor galaxies on the properties of\nsupernovae (SNe) and their host galaxies using 56 SNe located in pairs of\ngalaxies with different levels of star formation (SF) and nuclear activity. The\nmean distance of type II SNe from nuclei of hosts is greater by about a factor\nof 2 than that of type Ibc SNe. The distributions and mean distances of SNe are\nconsistent with previous results compiled with the larger sample. For the first\ntime it is shown that SNe Ibc are located in pairs with significantly smaller\ndifference of radial velocities between components than pairs containing SNe Ia\nand II. We consider this as a result of higher star formation rate (SFR) of\nthese closer systems of galaxies.", "category": "astro-ph_CO" }, { "text": "Optimal non-linear transformations for large scale structure statistics: Recently, several studies proposed non-linear transformations, such as a\nlogarithmic or Gaussianization transformation, as efficient tools to recapture\ninformation about the (Gaussian) initial conditions. During non-linear\nevolution, part of the cosmologically relevant information leaks out from the\nsecond moment of the distribution. This information is accessible only through\ncomplex higher order moments or, in the worst case, becomes inaccessible to the\nhierarchy. The focus of this work is to investigate these transformations in\nthe framework of Fisher information using cosmological perturbation theory of\nthe matter field with Gaussian initial conditions. We show that at each order\nin perturbation theory, there is a polynomial of corresponding order exhausting\nthe information on a given parameter. This polynomial can be interpreted as the\nTaylor expansion of the maximally efficient \"sufficient\" observable in the\nnon-linear regime. We determine explicitly this maximally efficient observable\nfor local transformations. Remarkably, this optimal transform is essentially\nthe simple power transform with an exponent related to the slope of the power\nspectrum; when this is -1, it is indistinguishable from the logarithmic\ntransform. This transform Gaussianizes the distribution, and recovers the\nlinear density contrast. Thus a direct connection is revealed between undoing\nof the non-linear dynamics and the efficient capture of Fisher information. Our\nanalytical results were compared with measurements from the Millennium\nSimulation density field. We found that our transforms remain very close to\noptimal even in the deeply non-linear regime with \\sigma^2 \\sim 10.", "category": "astro-ph_CO" }, { "text": "The Ultraluminous State: (Abridged) We revisit the question of the nature of ULXs through a detailed\ninvestigation of their spectral shape, using the highest quality X-ray data\navailable in the XMM-Newton public archives. We confirm that simple spectral\nmodels commonly used for the analysis and interpretation of ULXs (power-law\ncontinuum and multi-colour disc blackbody models) are inadequate in the face of\nsuch high quality data. Instead we find two near ubiquitous features in the\nspectrum: a soft excess and a roll-over in the spectrum at energies above 3keV.\nWe investigate a range of more physical models to describe these data. We find\nthat disc plus Comptonised corona models fit the data well, but the derived\ncorona is cool, and optically thick (tau ~ 5-30). We argue that these observed\ndisc temperatures are not a good indicator of the black hole mass as the\npowerful, optically thick corona drains energy from the inner disc, and\nobscures it. We estimate the intrinsic (corona-less) disc temperature, and\ndemonstrate that in most cases it lies in the regime of stellar mass black\nholes. These objects have spectra which range from those similar to the highest\nmass accretion rate states in Galactic binaries, to those which clearly have\ntwo peaks, one at energies below 1 keV (from the outer, unComptonised disc) and\none above 3 keV (from the Comptonised, inner disc). However, a few ULXs have a\nsignificantly cooler corrected disc temperature; we suggest that these are the\nmost extreme stellar mass black hole accretors, in which a massive wind\ncompletely envelopes the inner disc regions, creating a cool photosphere. We\nconclude that ULXs provide us with an observational template for the transition\nbetween Eddington and super-Eddington accretion flows, with the latter\noccupying a new ultraluminous accretion state.", "category": "astro-ph_CO" }, { "text": "Evidence for massive neutrinos from CMB and lensing observations: We discuss whether massive neutrinos (either active or sterile) can reconcile\nsome of the tensions within cosmological data that have been brought into focus\nby the recently released {\\it Planck} data. We point out that a discrepancy is\npresent when comparing the primary CMB and lensing measurements both from the\nCMB and galaxy lensing data using CFHTLenS, similar to that which arises when\ncomparing CMB measurements and SZ cluster counts. A consistent picture emerges\nand including a prior for the cluster constraints and BAOs we find that: for an\nactive neutrino model with 3 degenerate neutrinos, $\\sum m_{\\nu}= (0.320 \\pm\n0.081)\\,{\\rm eV}$, whereas for a sterile neutrino, in addition to 3 neutrinos\nwith a standard hierarchy and $\\sum m_{\\nu}= 0.06\\,{\\rm eV}$, $m_{\\nu, \\, \\rm\nsterile}^{\\rm eff}= (0.450 \\pm 0.124)\\,{\\rm eV}$ and $\\Delta N_{\\rm eff} = 0.45\n\\pm 0.23$. In both cases there is a significant detection of modification to\nthe neutrino sector from the standard model and in the case of the sterile\nneutrino it is possible to reconcile the BAO and local $H_0$ measurements.\nHowever, a caveat to our result is some internal tension between the CMB and\nlensing/cluster observations, and the masses are in excess of those estimated\nfrom the shape of the matter power spectrum from galaxy surveys.", "category": "astro-ph_CO" }, { "text": "Indirect Detection of Decaying Dark Matter with High Angular Resolution:\n Case for axion search by IRCS at Subaru Telescope: Recent advances in cosmic-ray detectors have provided exceptional\nsensitivities of dark matter with high angular resolution. Motivated by this,\nwe present a comprehensive study of cosmic-ray flux from dark matter decay in\ndwarf spheroidal galaxies (dSphs), with a focus on detectors possessing\narcsecond-level field of view and/or angular resolution. We propose to use\ndifferential $D$-factors, which are estimated for various dSphs since such\ndetectors are sensitive to their dark matter distributions. Our findings reveal\nthat the resulting signal flux can experience a more than $O$(1-10) enhancement\nwith different theoretical uncertainty compared to traditional estimations.\nBased on this analysis, we find that the Infrared Camera and Spectrograph\n(IRCS) installed on the 8.2m Subaru telescope can be a good dark matter\ndetector for the mass in the eV range, particularly axion-like particles\n(ALPs). Observing the Draco or Ursa Major II galaxies with the IRCS for just a\nfew nights will be sufficient to surpass the stellar cooling bounds for ALP\ndark matter with a mass in the range of $1\\,{\\rm eV} \\lesssim m_a \\lesssim\n2\\,\\rm eV$.", "category": "astro-ph_CO" }, { "text": "AGN feedback in galaxy groups: a joint GMRT/X-ray study: We present an ongoing study of 18 nearby galaxy groups, chosen for the\navailability of Chandra and/or XMM-Newton data and evidence for AGN/hot\nintragroup gas interaction. We have obtained 235 and 610 MHz observations at\nthe GMRT for all the groups, and 327 and 150 MHz for a few. We discuss two\ninteresting cases - NGC 5044 and AWM 4 - which exhibit different kinds of\nAGN/hot gas interaction. With the help of these examples we show how joining\nlow-frequency radio data (to track the history of AGN outbursts through\nemission from aged electron populations) with X-ray data (to determine the\nstate of hot gas, its disturbances, heating and cooling) can provide a unique\ninsight into the nature of the feedback mechanism in galaxy groups.", "category": "astro-ph_CO" }, { "text": "Phenomenological consequences of superfluid dark matter with\n baryon-phonon coupling: Recently, a new form of dark matter has been suggested to naturally reproduce\nthe empirically successful aspects of Milgrom's law in galaxies. The dark\nmatter particle candidates are axion-like, with masses of order eV and strong\nself-interactions. They Bose-Einstein condense into a superfluid phase in the\ncentral regions of galaxy halos. The superfluid phonon excitations in turn\ncouple to baryons and mediate an additional long-range force. For a suitable\nchoice of the superfluid equation of state, this force can mimic Milgrom's law.\nIn this paper we develop in detail some of the main phenomenological\nconsequences of such a formalism, by revisiting the expected dark matter halo\nprofile in the presence of an extended baryon distribution. In particular, we\nshow how rotation curves of both high and low surface brightness galaxies can\nbe reproduced, with a slightly rising rotation curve at large radii in massive\nhigh surface brightness galaxies, thus subtly different from Milgrom's law. We\nfinally point out other expected differences with Milgrom's law, in particular\nin dwarf spheroidal satellite galaxies, tidal dwarf galaxies, and globular\nclusters, whose Milgromian or Newtonian behavior depends on the position with\nrespect to the superfluid core of the host galaxy. We also expect ultra-diffuse\ngalaxies within galaxy clusters to have velocities slightly above the baryonic\nTully-Fisher relation. Finally, we note that, in this framework, photons and\ngravitons follow the same geodesics, and that galaxy-galaxy lensing, probing\nlarger distances within galaxy halos than rotation curves, should follow\npredictions closer to the standard cosmological model than those of Milgrom's\nlaw.", "category": "astro-ph_CO" }, { "text": "Cosmological Implications of the Tetron Model of Elementary Particles: Based on a possible solution to the tetron spin problem, a modification of\nthe standard Big Bang scenario is suggested, where the advent of a spacetime\nmanifold is connected to the appearance of tetronic bound states. The metric\ntensor is constructed from tetron constituents and the reason for cosmic\ninflation is elucidated. Furthermore, there are natural dark matter candidates\nin the tetron model. The ratio of ordinary to dark matter in the universe is\ncalculated to be 1:5.", "category": "astro-ph_CO" }, { "text": "Probing high-redshift quasars with ALMA. I. Expected observables and\n potential number of sources: (abridged) We explore how ALMA observations can probe high-redshift galaxies\nin unprecedented detail. We discuss the main observables that are excited by\nthe large-scale starburst, and formulate expectations for the chemistry and the\nfluxes in the center of active galaxies, where chemistry may be driven by the\nabsorption of X-ray photons. We show that such X-ray dominated regions (XDRs)\nshould be large enough to be resolved with ALMA, and predict the expected\namount of emission in CO and various fine-structure lines. We discuss how such\nXDRs can be distinguished from a strong starburst on the same spatial scales\nbased on the CO line SED. Our models are compared to known sources like NGC\n1068 and APM 08279. We also analyze the properties of the z=6.42 quasar SDSS\nJ114816.64+525150.3, and find that the observed emission in CO, [CII] and [CI]\nrequires a dense warm and a low-density cold gas component. We estimate the\nexpected number of sources at redshifts higher than 6, finding that one could\nexpect one black hole with $10^6$ solar masses per arcmin$^2$.", "category": "astro-ph_CO" }, { "text": "The Accretion Disc Particle Method for Simulations of Black Hole Feeding\n and Feedback: Black holes grow by accreting matter from their surroundings. However,\nangular momentum provides an efficient natural barrier to accretion and so only\nthe lowest angular momentum material will be available to feed the black holes.\nThe standard sub-grid model for black hole accretion in galaxy formation\nsimulations - based on the Bondi-Hoyle method - does not account for the\nangular momentum of accreting material, and so it is unclear how representative\nthe black hole accretion rate estimated in this way is likely to be. In this\npaper we introduce a new sub-grid model for black hole accretion that naturally\naccounts for the angular momentum of accreting material. Both the black hole\nand its accretion disc are modelled as a composite accretion disc particle. Gas\nparticles are captured by the accretion disc particle if and only if their\norbits bring them within its accretion radius R_acc, at which point their mass\nis added to the accretion disc and feeds the black hole on a viscous timescale\nt_visc. The resulting black hole accretion rate (dM/dt)_BH powers the accretion\nluminosity L_acc ~ (dM/dt)_BH, which drives black hole feedback. Using a series\nof controlled numerical experiments, we demonstrate that our new accretion disc\nparticle method is more physically self-consistent than the Bondi-Hoyle method.\nWe also discuss the physical implications of the accretion disc particle method\nfor systems with a high degree of rotational support, and we argue that the\nM_BH-sigma relation in these systems should be offset from the relation for\nclassical bulges and ellipticals, as appears to be observed.", "category": "astro-ph_CO" }, { "text": "A highly precise shear bias estimator independent of the measured shape\n noise: We present a new method to estimate shear measurement bias in image\nsimulations that significantly improves the precision with respect to current\ntechniques. Our method is based on measuring the shear response for individual\nimages. We generated sheared versions of the same image to measure how the\ngalaxy shape changes with the small applied shear. This shear response is the\nmultiplicative shear bias for each image. In addition, we also measured the\nindividual additive bias. Using the same noise realizations for each sheared\nversion allows us to compute the shear response at very high precision. The\nestimated shear bias of a sample of galaxies is then the average of the\nindividual measurements. The precision of this method leads to an improvement\nwith respect to previous methods concerned with the precision of estimates of\nmultiplicative bias since our method is not affected by noise from shape\nmeasurements, which until now has been the dominant uncertainty. As a\nconsequence, the method does not require shape-noise suppression for a precise\nestimation of shear multiplicative bias. Our method can be readily used for\nnumerous applications such as shear measurement validation and calibration,\nreducing the number of necessary simulated images by a few orders of magnitude\nto achieve the same precision.", "category": "astro-ph_CO" }, { "text": "Diffuse optical intracluster light as a measure of stellar tidal\n stripping: the cluster CL0024+17 at $z\\sim $0.4 observed at LBT: We have evaluated the diffuse intracluster light (ICL) in the central core of\nthe galaxy cluster CL0024+17 at $z\\sim 0.4$ observed with the prime focus\ncamera (LBC) at LBT. The measure required an accurate removal of the galaxies\nlight within $\\sim 200$ kpc from the center. The residual background intensity\nhas then been integrated in circular apertures to derive the average ICL\nintensity profile. The latter shows an approximate exponential decline as\nexpected from theoretical cold dark matter models. The radial profile of the\nICL over the galaxies intensity ratio (ICL fraction) is increasing with\ndecreasing radius but near the cluster center it starts to bend and then\ndecreases where the overlap of the halos of the brightest cluster galaxies\nbecomes dominant. Theoretical expectations in a simplified CDM scenario show\nthat the ICL fraction profile can be estimated from the stripped over galaxy\nstellar mass ratio in the cluster. It is possible to show that the latter\nquantity is almost independent of the properties of the individual host\ngalaxies but mainly depends on the average cluster properties. The predicted\nICL fraction profile is thus very sensitive to the assumed CDM profile, total\nmass and concentration parameter of the cluster. Adopting values very similar\nto those derived from the most recent lensing analysis in CL0024+17 we find a\ngood agreement with the observed ICL fraction profile. The galaxy counts in the\ncluster core have then been compared with that derived from composite cluster\nsamples in larger volumes, up to the clusters virial radius. The galaxy counts\nin the CL0024+17 core appear flatter and the amount of bending respect to the\naverage cluster galaxy counts imply a loss of total emissivity in broad\nagreement with the measured ICL fraction.", "category": "astro-ph_CO" }, { "text": "Are Newly Discovered HI High Velocity Clouds Minihalos in the Local\n Group?: A set of HI sources extracted from the north Galactic polar region by the\nongoing ALFALFA survey has properties that are consistent with the\ninterpretation that they are associated with isolated minihalos in the\noutskirts of the Local Group (LG). Unlike objects detected by previous surveys,\nsuch as the Compact High Velocity Clouds of Braun & Burton (1999), the HI\nclouds found by ALFALFA do not violate any structural requirements or halo\nscaling laws of the LambdaCDM structure paradigm, nor would they have been\ndetected by extant HI surveys of nearby galaxy groups other than the LG. At a\ndistance of d Mpc, their HI masses range between $5 x 10^4 d^2 and 10^6 d^2\nsolar and their HI radii between <0.4d and 1.6 d kpc. If they are parts of\ngravitationally bound halos, the total masses would be on order of 10^8--10^9\nsolar, their baryonic content would be signifcantly smaller than the cosmic\nfraction of 0.16 and present in a ionized gas phase of mass well exceeding that\nof the neutral phase. This study does not however prove that the minihalo\ninterpretation is unique. Among possible alternatives would be that the clouds\nare shreds of the Leading Arm of the Magellanic Stream.", "category": "astro-ph_CO" }, { "text": "Is the lack of power anomaly in the CMB correlated with the orientation\n of the Galactic plane?: The lack of power at large angular scales in the CMB temperature anisotropy\npattern is a feature known to depend on the size of the Galactic mask. Not only\nthe large scale anisotropy power in the CMB is lower than the best-fit\n$\\Lambda$CDM model predicts, but most of the power seems to be localised close\nto the Galactic plane, making high-Galactic latitude regions more anomalous. We\nassess how likely the latter behaviour is in a $\\Lambda$CDM model by extracting\nsimulations from the {\\it Planck} 2018 fiducial model. By comparing the former\nto {\\it Planck} data in different Galactic masks, we reproduce the anomaly\nfound in previous works, at a statistical significance of $\\sim 3 \\, \\sigma$.\nThis result suggests the existence of a bizzarre correlation between the\nparticular orientation of the Galaxy and the lack of power anomaly. To test\nthis hypothesis, we perform random rotations of the {\\it Planck} 2018 data and\ncompare these to similarly rotated $\\Lambda$CDM realisations. We find that,\namong all possible rotations, the lower-tail probability of the observed\nhigh-Galactic latitude data variance is still low at the level of $2.8 \\,\n\\sigma$. Furthermore, the lowering trend of the variance when moving from low-\nto high-Galactic latitude is anomalous in the data at $\\sim 3\\,\\sigma$ when\ncomparing to $\\Lambda$CDM rotated realisations. This shows that the lack of\npower at high Galactic latitude is substantially stable against the \"look\nelsewhere\" effect induced by random rotations of the Galaxy orientation.\nMoreover, this analysis turns out to be substantially stable if we employ, in\nplace of generic $\\Lambda$CDM simulations, a specific set whose variance is\nconstrained to reproduce the observed data variance.", "category": "astro-ph_CO" }, { "text": "cosmoabc: Likelihood-free inference via Population Monte Carlo\n Approximate Bayesian Computation: Approximate Bayesian Computation (ABC) enables parameter inference for\ncomplex physical systems in cases where the true likelihood function is\nunknown, unavailable, or computationally too expensive. It relies on the\nforward simulation of mock data and comparison between observed and synthetic\ncatalogues. Here we present cosmoabc, a Python ABC sampler featuring a\nPopulation Monte Carlo (PMC) variation of the original ABC algorithm, which\nuses an adaptive importance sampling scheme. The code is very flexible and can\nbe easily coupled to an external simulator, while allowing to incorporate\narbitrary distance and prior functions. As an example of practical application,\nwe coupled cosmoabc with the numcosmo library and demonstrate how it can be\nused to estimate posterior probability distributions over cosmological\nparameters based on measurements of galaxy clusters number counts without\ncomputing the likelihood function. cosmoabc is published under the GPLv3\nlicense on PyPI and GitHub and documentation is available at\nhttp://goo.gl/SmB8EX", "category": "astro-ph_CO" }, { "text": "A designer approach to $f(Q)$ gravity and cosmological implications: We investigate the evolution of linear perturbations in the Symmetric\nTeleparallel Gravity, namely $f(Q)$ gravity, for which we design the $f(Q)$\nfunction to match specific expansion histories. We consider different\nevolutions of the effective dark energy equation of state, $w_Q(a)$, which\nincludes $w_Q=-1$, a constant $w_Q \\neq -1$ and a fast varying equation of\nstate. We identify clear patterns in the effective gravitational coupling,\nwhich accordingly modifies the linear growth of large scale structures. We\nprovide theoretical predictions for the product of the growth rate $\\tilde{f}$\nand the root mean square of matter fluctuations $\\sigma_8$, namely\n$\\tilde{f}\\sigma_8$ and for the sign of the cross-correlation power spectrum of\nthe galaxy fluctuations and the cosmic microwave background radiation\nanisotropies. These properties can be used to distinguish the $f(Q)$ gravity\nfrom the standard cosmological model using accurate cosmological observations.", "category": "astro-ph_CO" }, { "text": "Accelerating MCMC algorithms through Bayesian Deep Networks: Markov Chain Monte Carlo (MCMC) algorithms are commonly used for their\nversatility in sampling from complicated probability distributions. However, as\nthe dimension of the distribution gets larger, the computational costs for a\nsatisfactory exploration of the sampling space become challenging. Adaptive\nMCMC methods employing a choice of proposal distribution can address this issue\nspeeding up the convergence. In this paper we show an alternative way of\nperforming adaptive MCMC, by using the outcome of Bayesian Neural Networks as\nthe initial proposal for the Markov Chain. This combined approach increases the\nacceptance rate in the Metropolis-Hasting algorithm and accelerate the\nconvergence of the MCMC while reaching the same final accuracy. Finally, we\ndemonstrate the main advantages of this approach by constraining the\ncosmological parameters directly from Cosmic Microwave Background maps.", "category": "astro-ph_CO" }, { "text": "Constraints on Cosmographic Functions of Cosmic Chronometers Data Using\n Gaussian Processes: We study observational constraints on the cosmographic functions up to the\nfourth derivative of the scale factor with respect to cosmic time, i.e., the\nso-called snap function, using the non-parametric method of Gaussian Processes.\nAs observational data we use the Hubble parameter data. Also we use mock data\nsets to estimate the future forecast and study the performance of this type of\ndata to constrain cosmographic functions. The combination between a\nnon-parametric method and the Hubble parameter data is investigated as a\nstrategy to reconstruct cosmographic functions. In addition, our results are\nquite general because they are not restricted to a specific type of functional\ndependency of the Hubble parameter. We investigate some advantages of using\ncosmographic functions instead of cosmographic series, since the former are\ngeneral definitions free of approximations. In general, our results do not\ndeviate significantly from $\\Lambda CDM$. We determine a transition redshift\n$z_{tr}=0.637^{+0.165}_{-0.175}$ and $H_{0}=69.45 \\pm 4.34$. Also assuming\npriors for the Hubble constant we obtain $z_{tr}=0.670^{+0.210}_{-0.120}$ with\n$H_{0}=67.44$ (Planck) and $z_{tr}=0.710^{+0.159}_{-0.111}$ with\n$H_{0}=74.03$(SH0ES). Our main results are summarized in table 2.", "category": "astro-ph_CO" }, { "text": "Observational Constraints on the Modified Gravity Model (MOG) Proposed\n by Moffat: Using the Magellanic System: A simple model for the dynamics of the Magellanic Stream (MS), in the\nframework of modified gravity models is investigated. We assume that the galaxy\nis made up of baryonic matter out of context of dark matter scenario. The model\nwe used here is named Modified Gravity (MOG) proposed by Moffat (2005). In\norder to examine the compatibility of the overall properties of the MS under\nthe MOG theory, the observational radial velocity profile of the MS is compared\nwith the numerical results using the $\\chi^2$ fit method. In order to obtain\nthe best model parameters, a maximum likelihood analysis is performed. We also\ncompare the results of this model with the Cold Dark Matter (CDM) halo model\nand the other alternative gravity model that proposed by Bekenstein (2004), so\ncalled TeVeS. We show that by selecting the appropriate values for the free\nparameters, the MOG theory seems to be plausible to explain the dynamics of the\nMS as well as the CDM and the TeVeS models.", "category": "astro-ph_CO" }, { "text": "A numerical study of pseudoscalar inflation with an axion-gauge field\n coupling: A numerical study of a pseudoscalar inflation having an axion-photon-like\ncoupling is performed by solving numerically the coupled differential equations\nof motion for inflaton and photon mode functions from the onset of inflation to\nthe end of reheating. The backreaction due to particle production is also\nincluded self-consistently. We find that this particular inflation model\nrealizes the idea of a warm inflation in which a steady thermal bath is\nestablished by the particle production. In most cases this thermal bath exceeds\nthe amount of radiation released in the reheating process. In the strong\ncoupling regime, the transition from the inflationary to the\nradiation-dominated phase does not involve either a preheating or reheating\nprocess. In addition, energy density peaks produced near the end of inflation\nmay lead to the formation of primordial black holes.", "category": "astro-ph_CO" }, { "text": "Higgs-induced spectroscopic shifts near strong gravity sources: We explore the consequences of the mass generation due to the Higgs field in\nstrong gravity astrophysical environments. The vacuum expectation value of the\nHiggs field is predicted to depend on the curvature of spacetime, potentially\ngiving rise to peculiar spectroscopic shifts, named hereafter \"Higgs shifts.\"\nHiggs shifts could be searched through dedicated multiwavelength and\nmultispecies surveys with high spatial and spectral resolution near strong\ngravity sources such as Sagittarius A* or broad searches for signals due to\nprimordial black holes. The possible absence of Higgs shifts in these surveys\nshould provide limits to the coupling between the Higgs particle and the\ncurvature of spacetime, a topic of interest for a recently proposed\nHiggs-driven inflationary model. We discuss some conceptual issues regarding\nthe coexistence between the Higgs mechanism and gravity, especially for their\ndifferent handling of fundamental and composite particles.", "category": "astro-ph_CO" }, { "text": "Exploring the Dark Universe: constraints on dynamical Dark Energy models\n from CMB, BAO and growth rate measurements: In order to explain the current acceleration of the Universe, the fine tuning\nproblem of the cosmological constant $\\Lambda$ and the cosmic coincidence\nproblem, different alternative models have been proposed in the literature. We\nuse the most recent observational data from CMB (Planck 2018 final data\nrelease) and LSS (SDSS, WiggleZ, VIPERS) to constrain dynamical dark energy\n(DE) models. The CMB shift parameter, which traditionally has been used to\ndetermine the main cosmological parameters of the standard model $\\Lambda CDM$\nis employed in addition to data from redshift-space distortions through the\ngrowth parameter $A(z)=f(z)\\sigma_{8}(z)$ to constrain the mass variance\n$\\sigma_{8}$. BAO data is also used to study the history of the cosmological\nexpansion and the main properties of DE. From the evolution of $q(z)$ we found\na slowdown of acceleration behaviour at low redshifts, and by using the Akaike\nand Bayesian Information Criterion (AIC, BIC) we discriminate different models\nthose that are better suited to the observational data, finding that the\ninteractive dark energy (IDE) model is the most favoured by observational data,\nincluding information from SNIa and Hz. The analysis shows that the IDE model\nis followed closely by EDE and $\\Lambda CDM$ models, which in some cases fit\nbetter the observational data with individual probes.", "category": "astro-ph_CO" }, { "text": "Constraint on Heavy Element Production in Inhomogeneous Big-Bang\n Nucleosynthesis from The Light-Element Observations: We investigate the observational constraints on the inhomogeneous big-bang\nnucleosynthesis that Matsuura et al. suggested the possibility of the heavy\nelement production beyond ${}^7$Li in the early universe. From the\nobservational constraints on light elements of ${}^4$He and D, possible regions\nare found on the plane of the volume fraction of the high density region\nagainst the ratio between high-and low-density regions. In these allowed\nregions, we have confirmed that the heavy elements beyond Ni can be produced\nappreciably, where $p$- and/or $r$-process elements are produced well\nsimultaneously.", "category": "astro-ph_CO" }, { "text": "The coordinated key role of wet, mixed, and dry major mergers in the\n buildup of massive early-type galaxies at z<~1: Hierarchical models predict that massive early-type galaxies (mETGs) derive\nfrom the most massive and violent merging sequences occurred in the Universe.\nHowever, the role of wet, mixed, and dry major mergers in the assembly of mETGs\nis questioned by some recent observations. We have developed a semi-analytical\nmodel to test the feasibility of the major-merger origin hypothesis for mETGs,\njust accounting for the effects on galaxy evolution of the major mergers\nstrictly reported by observations. The model proves that it is feasible to\nreproduce the observed number density evolution of mETGs since z~1, just\naccounting for the coordinated effects of wet/mixed/dry major mergers. It can\nalso reconcile the different assembly redshifts derived by hierarchical models\nand by mass downsizing data for mETGs, just considering that a mETG observed at\na certain redshift is not necessarily in place since then. The model predicts\nthat wet major mergers have controlled the mETGs buildup since z~1, although\ndry and mixed mergers have also played an essential role in it. The bulk of\nthis assembly took place at 0.71.0) galaxy clusters with mass measurements have\nbeen observed, spectroscopically confirmed and are reported in the literature.\nThese objects should be exceedingly rare in the standard LCDM model. We\nconservatively approximate the selection functions of these clusters' parent\nsurveys, and quantify the tension between the abundances of massive clusters as\npredicted by the standard LCDM model and the observed ones. We alleviate the\ntension considering non-Gaussian primordial perturbations of the local type,\ncharacterized by the parameter fnl and derive constraints on fnl arising from\nthe mere existence of these clusters. At the 95% confidence level, fnl>467 with\ncosmological parameters fixed to their most likely WMAP5 values, or fnl > 123\n(at 95% confidence) if we marginalize over WMAP5 parameters priors. In\ncombination with fnl constraints from Cosmic Microwave Background and halo\nbias, this determination implies a scale-dependence of fnl at approx. 3 sigma.\nGiven the assumptions made in the analysis, we expect any future improvements\nto the modeling of the non-Gaussian mass function, survey volumes, or selection\nfunctions to increase the significance of fnl>0 found here. In order to\nreconcile these massive, high-z clusters with an fnl=0, their masses would need\nto be systematically lowered by 1.5 sigma or the sigma8 parameter should be\napprox. 3 sigma higher than CMB (and large-scale structure) constraints. The\nexistence of these objects is a puzzle: it either represents a challenge to the\nLCDM paradigme or it is an indication that the mass estimates of clusters is\ndramatically more uncertain than we think.", "category": "astro-ph_CO" }, { "text": "Cosmological observations in the radio domain: the contribution of\n extragalactic sources: The low frequency tail of the CMB spectrum, down along the radio range (~1\nGHz), may carry weak spectral distortions which are fingerprints of processes\noccurred during different epochs of the thermal history of the Universe, from\nz~3\\times 10^6 to reionization. TRIS and ARCADE2 are the most recent\nexperiments dedicated to the exploration of this chapter of CMB cosmology. The\nlevel of instrumental accuracy they reached in the determination of the\nabsolute sky temperature is such that the removal of galactic and\nextra-galactic contamination is the true bottleneck towards the recovery of the\ncosmological signal. This will be certainly the case also for future\nexperiments in the radio domain. Here we present an update of a study\noriginally done to recognize the contribution of unresolved extra-galactic\nradio sources to the sky brightness measured by TRIS. Despite the specific\ncontext which originated our analysis, this is a study of general interest,\nimproved by the inclusion of all the source counts available up-to-date from\n150 MHz to 8.4 GHz.", "category": "astro-ph_CO" }, { "text": "Evolution of the $f\u03c3_8$ tension with the Planck15/$\u039b$CDM\n determination and implications for modified gravity theories: We construct an updated extended compilation of distinct (but possibly\ncorrelated) $f\\sigma_8(z)$ Redshift Space Distortion (RSD) data published\nbetween 2006 and 2018. It consists of 63 datapoints and is significantly larger\nthan previously used similar datasets. After fiducial model correction we\nobtain the best fit $\\Omega_{0m}-\\sigma_8$ $\\Lambda$CDM parameters and show\nthat they are at a $5\\sigma$ tension with the corresponding\nPlanck15/$\\Lambda$CDM values. Introducing a nontrivial covariance matrix\ncorrelating randomly $20\\%$ of the RSD datapoints has no significant effect on\nthe above tension level. We show that the tension disappears (becomes less than\n$1\\sigma$) when a subsample of the 20 most recently published data is used. A\npartial cause for this reduced tension is the fact that more recent data tend\nto probe higher redshifts (with higher errorbars) where there is degeneracy\namong different models due to matter domination. Allowing for a nontrivial\nevolution of the effective Newton's constant as\n$G_{\\textrm{eff}}(z)/G_{\\textrm{N}} = 1 + g_a \\left(\\frac{z}{1+z}\\right)^2 -\ng_a \\left(\\frac{z}{1+z}\\right)^4$ ($g_a$ is a parameter) and fixing a \\plcdm\nbackground we find $g_a=-0.91\\pm 0.17$ from the full $f\\sigma_8$ dataset while\nthe 20 earliest and 20 latest datapoints imply $g_a=-1.28^{+0.28}_{-0.26}$ and\n$g_a=-0.43^{+0.46}_{-0.41}$ respectively. Thus, the more recent $f\\sigma_8$\ndata appear to favor GR in contrast to earlier data. Finally, we show that the\nparametrization $f\\sigma_8(z)=\\lambda \\sigma_8 \\Omega(z)^\\gamma /(1+z)^\\beta$\nprovides an excellent fit to the solution of the growth equation for both GR\n($g_a=0$) and modified gravity ($g_a\\neq 0$).", "category": "astro-ph_CO" }, { "text": "Sensitivity and foreground modelling for large-scale CMB B-mode\n polarization satellite missions: The measurement of the large-scale B-mode polarization in the cosmic\nmicrowave background (CMB) is a fundamental goal of future CMB experiments.\nHowever, because of unprecedented sensitivity, future CMB experiments will be\nmuch more sensitive to any imperfect modelling of the Galactic foreground\npolarization in the reconstruction of the primordial B-mode signal. We compare\nthe sensitivity to B-modes of different concepts of CMB satellite missions\n(LiteBIRD, COrE, COrE+, PRISM, EPIC, PIXIE) in the presence of Galactic\nforegrounds. In particular, we quantify the impact on the tensor-to-scalar\nparameter of incorrect foreground modelling in the component separation\nprocess. Using Bayesian fitting and Gibbs sampling, we perform the separation\nof the CMB and Galactic foreground B-modes. The recovered CMB B-mode power\nspectrum is used to compute the likelihood distribution of the tensor-to-scalar\nratio. We focus the analysis to the very large angular scales that can be\nprobed only by CMB space missions, i.e. the Reionization bump, where primordial\nB-modes dominate over spurious B-modes induced by gravitational lensing. We\nfind that fitting a single modified blackbody component for thermal dust where\nthe \"real\" sky consists of two dust components strongly bias the estimation of\nthe tensor-to-scalar ratio by more than 5{\\sigma} for the most sensitive\nexperiments. Neglecting in the parametric model the curvature of the\nsynchrotron spectral index may bias the estimated tensor-to-scalar ratio by\nmore than 1{\\sigma}. For sensitive CMB experiments, omitting in the foreground\nmodelling a 1% polarized spinning dust component may induce a non-negligible\nbias in the estimated tensor-to-scalar ratio.", "category": "astro-ph_CO" }, { "text": "Constraints on turbulent pressure in the X-ray halos of giant elliptical\n galaxies from resonant scattering: The dense cores of X-ray emitting gaseous halos of large elliptical galaxies\nwith temperatures below about 0.8 keV show two prominent Fe XVII emission\nfeatures, which provide a sensitive diagnostic tool to measure the effects of\nresonant scattering. We present here high-resolution spectra of five bright\nnearby elliptical galaxies, obtained with the Reflection Grating Spectrometers\n(RGS) on the XMM-Newton satellite. The spectra for the cores of four of the\ngalaxies show the Fe XVII line at 15.01 Angstrom being suppressed by resonant\nscattering. The data for NGC 4636 in particular allow the effects of resonant\nscattering to be studied in detail and to prove that the 15.01 Angstrom line is\nsuppressed only in the dense core and not in the surrounding regions. Using\ndeprojected density and temperature profiles for this galaxy obtained with the\nChandra satellite, we model the radial intensity profiles of the strongest\nresonance lines, accounting for the effects of resonant scattering, for\ndifferent values of the characteristic turbulent velocity. Comparing the model\nto the data, we find that the isotropic turbulent velocities on spatial scales\nsmaller than about 1 kpc are less than 100 km/s and the turbulent pressure\nsupport in the galaxy core is smaller than 5% of the thermal pressure at the\n90% confidence level, and less than 20% at 95% confidence. Neglecting the\neffects of resonant scattering in spectral fitting of the inner 2 kpc core of\nNGC 4636 will lead to underestimates of the chemical abundances of Fe and O by\n~10-20%.", "category": "astro-ph_CO" }, { "text": "Primordial Non-Gaussianity from G-inflation: Enormous information about interactions is contained in the non-Gaussianities\nof the primordial curvature perturbations, which are essential to break the\ndegeneracy of inflationary models. We study the primordial bispectra for\nG-inflation models predicting both sharp and broad peaks in the primordial\nscalar power spectrum. We calculate the non-Gaussianity parameter\n$f_{\\mathrm{NL}}$ in the equilateral limit and squeezed limit numerically, and\nconfirm that the consistency relation holds in these models. Even though\n$f_{\\mathrm{NL}}$ becomes large at the scales before the power spectrum reaches\nthe peak and the scales where there are wiggles in the power spectrum, it\nremains to be small at the peak scales. Therefore, the contributions of\nnon-Gaussianity to the scalar induced secondary gravitational waves and\nprimordial black hole abundance are expected to be negligible.", "category": "astro-ph_CO" }, { "text": "The evolution of the AGN content in groups up to z~1: Determining the AGN content in structures of different mass/velocity\ndispersion and comparing them to higher mass/lower redshift analogs is\nimportant to understand how the AGN formation process is related to\nenvironmental properties. We use our well-tested cluster finding algorithm to\nidentify structures in the GOODS North and South fields, exploiting the\navailable spectroscopic redshifts and accurate photometric redshifts. We\nidentify 9 structures in GOODS-south (presented in a previous paper) and 8 new\nstructures in GOODS-north. We only consider structures where at least 2/3 of\nthe members brighter than M_R=-20 have a spectroscopic redshift. For those\ngroup members that coincide with X-ray sources in the 4 and 2 Msec Chandra\nsource catalogs respectively, we determine if the X-ray emission originates\nfrom AGN activity or it is related to the galaxies' star-formation activity. We\nfind that the fraction of AGN with Log L_H > 42 erg/s in galaxies with M_R <\n-20 is on average 6.3+-1.3%, much higher than in lower redshift groups of\nsimilar mass and more than double the fraction found in massive clusters at a\nsimilarly high redshift. We then explore the spatial distribution of AGN in the\nstructures and find that they preferentially populate the outer regions. The\ncolors of AGN host galaxies in structures tend to be confined to the green\nvalley, thus avoiding the blue cloud and, partially, also the red-sequence,\ncontrary to what happens in the field. We finally compare our results to the\npredictions of two sets of semi analytic models to investigate the evolution of\nAGN and evaluate potential triggering and fueling mechanisms. The outcome of\nthis comparison attests the importance of galaxy encounters, not necessarily\nleading to mergers, as an efficient AGN triggering mechanism. (abridged)", "category": "astro-ph_CO" }, { "text": "A Wide-field High Resolution HI Mosaic of Messier 31: I. Opaque Atomic\n Gas and Star Formation Rate Density: We have undertaken a deep, wide-field HI imaging survey of M31, reaching a\nmaximum resolution of about 50 pc and 2 km/s across a 95x48 kpc region. The HI\nmass and brightness sensitivity at 100 pc resolution for a 25 km/s wide\nspectral feature is 1500 M_Sun and 0.28 K. Our study reveals ubiquitous HI\nself-opacity features, discernible in the first instance as filamentary local\nminima in images of the peak HI brightness temperature. Local minima are\norganized into complexes of more than kpc length and are particularly\nassociated with the leading edge of spiral arm features. Just as in the Galaxy,\nthere is only patchy correspondence of self-opaque features with CO(1-0)\nemission. Localized opacity corrections to the column density exceed an order\nof magnitude in many cases and add globally to a 30% increase in the atomic gas\nmass over that inferred from the integrated brightness under the usual\nassumption of negligible self-opacity. Opaque atomic gas first increases from\n20 to 60 K in spin temperature with radius to 12 kpc but then declines again to\n20 K beyond 25 kpc. We have extended the resolved star formation law down to\nphysical scales more than an order of magnitude smaller in area and mass than\nhas been possible previously. The relation between total-gas-mass- and\nstar-formation-rate-density is significantly tighter than that with\nmolecular-mass and is fully consistent in both slope and normalization with the\npower law index of 1.56 found in the molecule-dominated disk of M51 at 500 pc\nresolution. Below a gas-mass-density of about 5 M_Sun/pc^2, there is a\ndown-turn in star-formation-rate-density which may represent a real local\nthreshold for massive star formation at a cloud mass of about 5x10^4 M_Sun.", "category": "astro-ph_CO" }, { "text": "A note on Low Energy Effective Theory of Chromo Natural Inflation in the\n light of BICEP2 results: Recent result of BICEP2, revealing a larger value of tensor to scalar ratio\n(r), has opened up new investigations of the in ationary models to fit the\nexperimental data. The experiment needs to reconfirm the results, specifically\nthe consistency between Planck and BICEP2. On the other hand, the combined\nanalysis of Planck and BICEP2 B, including the dust polarization uncertainty,\nbrings down the upper limit on r. In this note, we reexamine the low energy\neffective theory of Chromo Natural In ation model and its generalization in\nview of such observational data. We find that the parameter space of the model\nadmits a large value of r as well as other cosmological observables consistent\nwith data.", "category": "astro-ph_CO" }, { "text": "The impact of the SZ effect on cm-wavelength (1-30 GHz) observation of\n galaxy cluster radio relics: (Abridged) Radio relics in galaxy clusters are believed to be associated with\npowerful shock fronts that originate during cluster mergers, and are a testbed\nfor the acceleration of relativistic particles in the intracluster medium.\nRecently, radio relic observations have pushed into the cm-wavelength domain\n(1-30 GHz) where a break from the standard synchrotron power-law spectrum has\nbeen found, most noticeably in the famous 'Sausage' relic. In this paper, we\npoint to an important effect that has been ignored or considered insignificant\nwhile interpreting these new high-frequency radio data, namely the\ncontamination due to the Sunyaev-Zel'dovich (SZ) effect that changes the\nobserved synchrotron flux. Even though the radio relics reside in the cluster\noutskirts, the shock-driven pressure boost increases the SZ signal locally by\nroughly an order of magnitude. The resulting flux contamination for some\nwell-known relics are non-negligible already at 10 GHz, and at 30 GHz the\nobserved synchrotron fluxes can be diminished by a factor of several from their\ntrue values. Interferometric observations are not immune to this contamination,\nsince the change in the SZ signal occurs roughly at the same length scale as\nthe synchrotron emission, although there the flux loss is less severe than\nsingle-dish observations. We present a simple analytical approximation for the\nsynchrotron-to-SZ flux ratio, based on a theoretical radio relic model that\nconnects the non-thermal emission to the thermal gas properties, and show that\nby measuring this ratio one can potentially estimate the relic magnetic fields\nor the particle acceleration efficiency.", "category": "astro-ph_CO" }, { "text": "A high-resolution self-consistent whole sky foreground model: The neutral hydrogen 21cm line is potentially a very powerful probe of the\nobservable universe, and a number of on-going experiments are trying to detect\nit at cosmological distances. However, the presence of strong foreground\nradiations such as the galactic synchrotron radiation, galactic free-free\nemission and extragalactic radio sources make it a very challenging task. For\nthe design of 21cm experiments and analysis of their data, simulation is an\nessential tool, and good sky foreground model is needed. With existing data the\nwhole sky maps are available only in low angular resolutions or for limited\npatches of sky, which is inadequate in the simulation of these new 21cm\nexperiments. In this paper, we present the method of constructing a high\nresolution self-consistent sky model at low frequencies, which incorporates\nboth diffuse foreground and point sources. Our diffuse map is constructed by\ngenerating physical foreground components including the galactic synchrotron\nemission and galactic free-free emission. The point source sample is generated\nusing the actual data from the NRAO VLA Sky Survey (NVSS) and the Sydney\nUniversity Molonglo Sky Survey (SUMSS) where they are available and complete in\nflux limit, and mock point sources according to statistical distributions. The\nentire model is made self-consistent by removing the integrated flux of the\npoint sources from the diffuse map so that this part of radiation is not double\ncounted. We show that with the point sources added, a significant angular power\nis introduced in the mock sky map, which may be important for foreground\nsubtraction simulations. Our sky maps and point source catalogues are available\nto download.", "category": "astro-ph_CO" }, { "text": "The Sloan Great Wall. Rich clusters: We present the results of the study of the substructure and galaxy content of\nten rich clusters of galaxies in three different superclusters of the Sloan\nGreat Wall. We determine the substructure in clusters using the 'Mclust'\npackage from the 'R' statistical environment and analyse their galaxy content.\nWe analyse the distribution of the peculiar velocities of galaxies in clusters\nand calculate the peculiar velocity of the first ranked galaxy. We show that\nclusters in our sample have more than one component; in some clusters different\ncomponents also have different galaxy content. We find that in some clusters\nwith substructure the peculiar velocities of the first ranked galaxies are\nlarge. All clusters in our sample host luminous red galaxies. They can be found\nboth in the central areas of clusters as well as in the outskirts, some of them\nhave large peculiar velocities. About 1/3 of red galaxies in clusters are\nspirals. The scatter of colours of red ellipticals is in most clusters larger\nthan that of red spirals. The presence of substructure in rich clusters, signs\nof possible mergers and infall, as well as the large peculiar velocities of the\nfirst ranked galaxies suggest that the clusters in our sample are not yet\nvirialized. We present merger trees of dark matter haloes in an N-body\nsimulation to demonstrate the formation of present-day dark matter haloes via\nmultiple mergers during their evolution. In simulated dark matter haloes we\nfind a substructure similar to that in observed clusters.", "category": "astro-ph_CO" }, { "text": "Ghost Collapse : exploring feasibility of spurious Spherical Collapses: We explore the real solutions to the Spherical Collapse Model in a non-flat\nUniverse with a Cosmological Constant, and observe a possible situation for a\nfake or Ghost Collapse, in which an expanding overdense spherical region, turns\naround and begins to collapse, turns around again after a finite time and\nstarts expanding. To make such a situation of spurious collapse feasible, we\nmake a linear redshift dependent correction to the standard Dark Energy density\nterm which is originally in the form of a cosmological constant. There is good\nreason to believe in such a correction based on recent research which hints\nthat Dark Energy desnity evolves with the redshift (even becomes negative) when\nfit to observational data.", "category": "astro-ph_CO" }, { "text": "Observational signatures of microlensing in gravitational waves at\n LIGO/Virgo frequencies: Microlenses with typical stellar masses (a few ${\\rm M}_{\\odot}$) have\ntraditionally been disregarded as potential sources of gravitational lensing\neffects at LIGO/Virgo frequencies, since the time delays are often much smaller\nthan the inverse of the frequencies probed by LIGO/Virgo, resulting in\nnegligible interference effects at LIGO/Virgo frequencies. While this is true\nfor isolated microlenses in this mass regime, we show how, under certain\ncircumstances and for realistic scenarios, a population of microlenses (for\ninstance stars and remnants from a galaxy halo or from the intracluster medium)\nembedded in a macromodel potential (galaxy or cluster) can conspire together to\nproduce time delays of order one millisecond which would produce significant\ninterference distortions in the observed strains. At sufficiently large\nmagnification factors (of several hundred), microlensing effects should be\ncommon in gravitationally lensed gravitational waves. We explore the regime\nwhere the predicted signal falls in the frequency range probed by LIGO/Virgo.\nWe find that stellar mass microlenses, permeating the lens plane, and near\ncritical curves, can introduce interference distortions in strongly lensed\ngravitational waves. For those lensed events with negative parity, (or saddle\npoints, never studied before in the context of gravitational waves), and that\ntake place near caustics of macromodels, they are more likely to produce\nmeasurable interference effects at LIGO/Virgo frequencies. This is the first\nstudy that explores the effect of a realistic population of microlenses, plus a\nmacromodel, on strongly lensed gravitational waves.", "category": "astro-ph_CO" }, { "text": "Beyond Concordance Cosmology with Magnification of Gravitational-Wave\n Standard Sirens: We show how future gravitational-wave detectors would be able of\ndiscriminating between the concordance LCDM cosmological model and up-to-date\ncompeting alternatives, e.g. dynamical dark energy models (DE) or modified\ngravity theories (MG). Our method consists in using the weak-lensing\nmagnification effect that affects a standard-siren signal because of its\ntravelling trough the Universe's large-scale structure. As a demonstration, we\npresent constraints on DE and MG from proposed gravitational-wave detectors,\nnamely ET and DECIGO/BBO.", "category": "astro-ph_CO" }, { "text": "The deconvolved distribution estimator: enhancing reionisation-era CO\n line-intensity mapping analyses with a cross-correlation analogue for\n one-point statistics: We present the deconvolved distribution estimator (DDE), an extension of the\nvoxel intensity distribution (VID), in the context of future observations\nproposed as part of the CO Mapping Array Project (COMAP). The DDE exploits the\nfact that the observed VID is a convolution of correlated signal intensity\ndistributions and uncorrelated noise or interloper intensity distributions. By\ndeconvolving the individual VID of two observables away from their joint VID in\na Fourier-space operation, the DDE suppresses sensitivity to interloper\nemission while maintaining sensitivity to correlated components. The DDE thus\nimproves upon the VID by reducing the relative influence of uncorrelated noise\nand interloper biases, which is useful in the context of COMAP observations\nthat observe different rotational transitions of CO from the same comoving\nvolume in different observing frequency bands. Fisher forecasts suggest that\nthe theoretical sensitivity in the DDE allows significant improvements in\nconstraining power compared to either the cross power spectrum or the\nindividual VID data, and matches the constraining power of the combination of\nall other one- and two-point summary statistics. Future work should further\ninvestigate the covariance and model-dependent behaviour of this novel\none-point cross-correlation statistic.", "category": "astro-ph_CO" }, { "text": "The Physics and Mass Assembly of distant galaxies with the E-ELT: One of the main science goal of the future European Extremely Large Telescope\nwill be to understand the mass assembly process in galaxies as a function of\ncosmic time. To this aim, a multi-object, AO-assisted integral field\nspectrograph will be required to map the physical and chemical properties of\nvery distant galaxies. In this paper, we examine the ability of such an\ninstrument to obtain spatially resolved spectroscopy of a large sample of\nmassive (0.15) redshift bin. We\nfind that a survey of Ngal galaxies that fulfil the range of science goals can\nbe achieved with a ~90 nights program on the E-ELT, provided a multiplex\ncapability M Ngal/8.", "category": "astro-ph_CO" }, { "text": "Exploring the Impact of Microlensing on Gravitational Wave Signals:\n Biases, Population Characteristics, and Prospects for Detection: In this study, we investigate the impact of microlensing on gravitational\nwave (GW) signals in the LIGO$-$Virgo sensitivity band. Microlensing caused by\nan isolated point lens, with (redshifted) mass ranging from\n$M_\\mathrm{Lz}\\in(1,10^5){\\rm M}_\\odot$ and impact parameter $y\\in (0.01,~5)$,\ncan result in a maximum mismatch of $\\sim 30\\%$ with their unlensed\ncounterparts. When $y<1$, it strongly anti-correlates with the luminosity\ndistance enhancing the detection horizon and signal-to-noise ratio (SNR).\nBiases in inferred source parameters are assessed, with in-plane spin\ncomponents being the most affected intrinsic parameters. The luminosity\ndistance is often underestimated, while sky-localisation and trigger times are\nmostly well-recovered. Study of a population of microlensed signals due to an\nisolated point lens primarily reveals: (i) using unlensed templates during the\nsearch causes fractional loss ($20\\%$ to $30\\%$) of potentially identifiable\nmicrolensed signals; (ii) the observed distribution of $y$ challenges the\nnotion of its high improbability at low values ($y\\lesssim 1$), especially for\n$y\\lesssim 0.1$; (iii) Bayes factor analysis of the population indicates that\ncertain region in $M_\\mathrm{Lz}-y$ parameter space have a higher probability\nof being detected and accurately identified as microlensed. Notably, the\nmicrolens parameters for the most compelling candidate identified in previous\nmicrolensing searches, GW200208_130117, fall within a 1-sigma range of the\naforementioned higher probability region. Identifying microlensing signatures\nfrom $M_\\mathrm{Lz}<100~$M$_\\odot$ remains challenging due to small\nmicrolensing effects at typical SNR values. Additionally, we also examined how\nmicrolensing from a population of microlenses influences the detection of\nstrong lensing signatures in pairs of GW events, particularly in the\nposterior-overlap analysis.", "category": "astro-ph_CO" }, { "text": "Can varying the gravitational constant alleviate the tensions ?: Constraints on the cosmological concordance model parameters from observables\nat different redshifts are usually obtained using the locally measured value of\nthe gravitational constant $G_N$. Here we relax this assumption, by considering\n$G$ as a free parameter, either constant over the redshift range or dynamical\nbut limited to differ from fiducial value only above a certain redshift. Using\nCMB data and distance measurements from galaxy clustering BAO feature, we\nconstrain the cosmological parameters, along with $G$, through a MCMC bayesian\ninference method. Furthermore, we investigate whether the tensions on the\nmatter fluctuation $\\sigma_8$ and Hubble $H_0$ parameter could be alleviated by\nthis new variable. We used different parameterisations spanning from a constant\n$G$ to a dynamical $G$. In all the cases investigated in this work we found no\nmechanism that alleviates the tensions when both CMB and BAO data are used with\n$\\xi_{\\mathrm{g}} = G / G_N$ constrained to 1.0$\\pm0.04$ (resp. $\\pm0.01$) in\nthe constant (resp. dynamical) case. Finally, we studied the cosmological\nconsequences of allowing a running of the spectral index, since the later is\nsensitive to a change in $G$. For the two parameterisations adopted, we found\nno significant changes to the previous conclusions.", "category": "astro-ph_CO" }, { "text": "Quasi-periodical features in the distribution of Luminous Red Galaxies: A statistical analysis of radial distributions of Luminous Red Galaxies\n(LRGs) from the Sloan Digital Sky Survey (SDSS DR7) catalogue within an\ninterval $0.16 \\leq z \\leq 0.47$ is carried out. We found that the radial\ndistribution of $\\sim$ 106,000 LRGs incorporates a few quasi-periodical\ncomponents relatively to a variable $\\eta$, dimensionless line-of-sight\ncomoving distance calculated for the $\\Lambda$CDM cosmological model. The most\nsignificant peaks of the power spectra are obtained for two close periodicities\ncorresponding to the spatial comoving scales $(135 \\pm 12) h^{-1}$ Mpc and\n$(101 \\pm 6)h^{-1}$ Mpc. The latter one is dominant and consistent with the\ncharacteristic scale of the baryon acoustic oscillations. We analyse also the\nradial distributions of two other selected LRG samples: $\\sim$ 33,400 bright\nLRGs ($-23.2 < M \\leq -21.8$) and $\\sim$ 60,300 all LRGs within a rectangle\nregion on the sky, and show differences of the quasi-periodical features\ncharacteristic for different samples. Being confirmed the results would allow\nto give preference of the spatial against temporal models which could explain\nthe quasi-periodicities discussed here. As a caveat we show that estimations of\nthe significance levels of the peaks strongly depend on a smoothed radial\nfunction (trend) as well as characteristics of random fluctuations.", "category": "astro-ph_CO" }, { "text": "Full covariance of CMB and lensing reconstruction power spectra: CMB and lensing reconstruction power spectra are powerful probes of\ncosmology. However they are correlated, since the CMB power spectra are lensed\nand the lensing reconstruction is constructed using CMB multipoles. We perform\na full analysis of the auto- and cross-covariances, including polarization\npower spectra and minimum variance lensing estimators, and compare with\nsimulations of idealized future CMB-S4 observations. Covariances sourced by\nfluctuations in the unlensed CMB and instrumental noise can largely be removed\nby using a realization-dependent subtraction of lensing reconstruction noise,\nleaving a relatively simple covariance model that is dominated by\nlensing-induced terms and well described by a small number of principal\ncomponents. The correlations between the CMB and lensing power spectra will be\ndetectable at the level of $\\sim 5\\sigma$ for a CMB-S4 mission, and neglecting\nthose could underestimate some parameter error bars by several tens of percent.\nHowever we found that the inclusion of external priors or data sets to estimate\nparameter error bars can make the impact of the correlations almost negligible.", "category": "astro-ph_CO" }, { "text": "A robust upper limit on N_eff from BBN, circa 2011: We derive here a robust bound on the effective number of neutrinos from\nconstraints on primordial nucleosynthesis yields of deuterium and helium. In\nparticular, our results are based on very weak assumptions on the astrophysical\ndetermination of the helium abundance, namely that the minimum effect of\nstellar processing is to keep constant (rather than increase, as expected) the\nhelium content of a low-metallicity gas. Using the results of a recent analysis\nof extragalactic HII regions as upper limit, we find that Delta Neff<= 1 at 95\n% C.L., quite independently of measurements on the baryon density from cosmic\nmicrowave background anisotropy data and of the neutron lifetime input. In our\napproach, we also find that primordial nucleosynthesis alone has no significant\npreference for an effective number of neutrinos larger than the standard value.\nThe ~2 sigma hint sometimes reported in the literature is thus driven by CMB\ndata alone and/or is the result of a questionable regression protocol to infer\na measurement of primordial helium abundance.", "category": "astro-ph_CO" }, { "text": "Modification of the halo mass function by kurtosis associated with\n primordial non-Gaussianity: We study the halo mass function in the presence of the kurtosis type of\nprimordial non-Gaussianity. The kurtosis corresponds to the trispectrum as\ndefined in Fourier space. The primordial trispectrum is commonly characterized\nby two parameters, $\\tau_{\\rm NL}$ and $g_{\\rm NL}$. As applications of the\nderived non-Gaussian mass function, we consider the effect on the abundance of\nvoid structure, the effect on early star formation and on formation of the most\nmassive object at high redshift. We show that by comparing the effects of\nprimordial non-Gaussianity on cluster abundance with that on void abundance, we\ncan distinguish between the skewness and the kurtosis types of primordial\nnon-Gaussianity. As for early star formation, we show that the kurtosis type of\nprimordial non-Gaussianity seems not to affect the reionization history of the\nUniverse on average. However, at high redshifts (up to $z\\simeq 20$) such\nnon-Gaussianity does somewhat affect the early stages of reionization.", "category": "astro-ph_CO" }, { "text": "Dusty MgII Absorbers: Implications for the GRB/Quasar Incidence\n Discrepancy: There is nearly a factor of four difference in the number density of\nintervening MgII absorbers as determined from gamma-ray burst (GRB) and quasar\nlines of sight. We use a Monte-Carlo simulation to test if a dust extinction\nbias can account for this discrepancy. We apply an empirically determined\nrelationship between dust column density and MgII rest equivalent width to\nsimulated quasar sight-lines and model the underlying number of quasars that\nmust be present to explain the published magnitude distribution of SDSS\nquasars. We find that an input MgII number density dn/dz of 0.273 +- 0.002 over\nthe range 0.4 <= z <= 2.0 and with MgII equivalent width W_0 >= 1.0 angstroms\naccurately reproduces observed distributions. From this value, we conclude that\na dust obstruction bias cannot be the sole cause of the observed discrepancy\nbetween GRB and quasar sight-lines: this bias is likely to reduce the\ndiscrepancy only by ~10%.", "category": "astro-ph_CO" }, { "text": "Primordial power spectrum: a complete analysis with the WMAP nine-year\n data: We have improved further the error sensitive Richardson-Lucy deconvolution\nalgorithm making it applicable directly on the un-binned measured angular power\nspectrum of Cosmic Microwave Background observations to reconstruct the form of\nthe primordial power spectrum. This improvement makes the application of the\nmethod significantly more straight forward by removing some intermediate stages\nof analysis allowing a reconstruction of the primordial spectrum with higher\nefficiency and precision and with lower computational expenses. Applying the\nmodified algorithm we fit the WMAP 9 year data using the optimized\nreconstructed form of the primordial spectrum with more than 300 improvement in\n\\chi^2 with respect to the best fit power-law. This is clearly beyond the reach\nof other alternative approaches and reflects the efficiency of the proposed\nmethod in the reconstruction process and allow us to look for any possible\nfeature in the primordial spectrum projected in the CMB data. Though the\nproposed method allow us to look at various possibilities for the form of the\nprimordial spectrum, all having good fit to the data, proper error-analysis is\nneeded to test for consistency of theoretical models since, along with possible\nphysical artefacts, most of the features in the reconstructed spectrum might be\narising from fitting noises in the CMB data. Reconstructed error-band for the\nform of the primordial spectrum using many realizations of the data, all\nbootstrapped and based on WMAP 9 year data, shows proper consistency of\npower-law form of the primordial spectrum with the WMAP 9 data at all wave\nnumbers. Including WMAP polarization data in to the analysis have not improved\nmuch our results due to its low quality but we expect Planck data will allow us\nto make a full analysis on CMB observations on both temperature and\npolarization separately and in combination.", "category": "astro-ph_CO" }, { "text": "Fantasia of a Superfluid Universe -- In memory of Kerson Huang: This article introduces Kerson Huang's theory on superfluid universe in these\naspects: I. choose the asymptotically free Halpern-Huang scalar field(s) to\ndrive inflation; II. use quantum turbulence to create matter; III. consider\ndark energy as the energy density of the cosmic superfluid and dark matter the\ndeviation of the superfluid density from its equilibrium value; IV. use quantum\nvorticity to explain phenomena such as the non-thermal filaments at the\ngalactic center, the large voids in the galactic distribution, and the\ngravitational collapse of stars to fast-rotating blackholes.", "category": "astro-ph_CO" }, { "text": "Spectral distortions in the cosmic microwave background polarization: We compute the spectral distortions of the Cosmic Microwave Background (CMB)\npolarization induced by non-linear effects in the Compton interactions between\nCMB photons and cold intergalactic electrons. This signal is of the $y$-type\nand is dominated by contributions arising from the reionized era. We stress\nthat it is not shadowed by the thermal SZ effect which has no equivalent for\npolarization. We decompose its angular dependence into $E$- and $B$-modes, and\nwe calculate the corresponding power spectra, both exactly and using a suitable\nLimber approximation that allows a simpler numerical evaluation. We find that\n$B$-modes are of the same order of magnitude as $E$-modes. Both spectra are\nrelatively flat, peaking around $\\ell=280$, and their overall amplitude is\ndirectly related to the optical depth to reionization. Moreover, we find this\neffect to be one order of magnitude larger than the non-linear kinetic\nSunyaev-Zel'dovich effect in galaxy clusters. Finally, we discuss how to\nimprove the detectability of our signal by cross-correlating it with other\nquantities sourced by the flow of intergalactic electrons.", "category": "astro-ph_CO" }, { "text": "Evidence of major dry mergers at M* > 2 x 10^11 Msun from curvature in\n early-type galaxy scaling relations?: For early-type galaxies, the correlations between stellar mass and size,\nvelocity dispersion, surface brightness, color, axis ratio and color-gradient\nall indicate that two mass scales, M* = 3 x 10^10 Msun and M* = 2 x 10^11 Msun,\nare special. The smaller scale could mark the transition between wet and dry\nmergers, or it could be related to the interplay between SN and AGN feedback,\nalthough quantitative measures of this transition may be affected by\nmorphological contamination. At the more massive scale, mean axis ratios and\ncolor gradients are maximal, and above it, the colors are redder, the sizes\nlarger and the velocity dispersions smaller than expected based on the scaling\nat lower M*. In contrast, the color-sigma relation, and indeed, most scaling\nrelations with sigma, are not curved: they are well-described by a single power\nlaw, or in some cases, are almost completely flat. When major dry mergers\nchange masses, sizes, axis ratios and color gradients, they are expected to\nchange the colors or velocity dispersions much less. Therefore, the fact that\nscaling relations at sigma > 150 km/s show no features, whereas the size-M*,\nb/a-M*, color-M* and color gradient-M* relations do, suggests that M* = 2 x\n10^11 Msun is the scale above which major dry mergers dominate the assembly\nhistories of early-type galaxies.", "category": "astro-ph_CO" }, { "text": "Baryonic effects on weak-lensing two-point statistics and its\n cosmological implications: We develop an extension of \\textit{the Halo Model} that describes\nanalytically the corrections to the matter power spectrum due to the physics of\nbaryons. We extend these corrections to the weak-lensing shear angular power\nspectrum. Within each halo, our baryonic model accounts for: 1) a central\ngalaxy, the major stellar component whose properties are derived from abundance\nmatching techniques; 2) a hot plasma in hydrostatic equilibrium and 3) an\nadiabatically-contracted dark matter component. This analytic approach allows\nus to compare our model to the dark-matter-only case. Our basic assumptions are\ntested against the hydrodynamical simulations of Martizzi et. al. (2014), with\nwhich a remarkable agreement is found. Our baryonic model has only one free\nparameter, $M_{\\rm crit}$, the critical halo mass that marks the transition\nbetween feedback-dominated halos, mostly devoid of gas, and gas rich halos, in\nwhich AGN feedback effects become weaker. We explore the entire cosmological\nparameter space, using the angular power spectrum in three redshift bins as the\nobservable, assuming a Euclid-like survey. We derive the corresponding\nconstraints on the cosmological parameters, as well as the possible bias\nintroduced by neglecting the effects of baryonic physics. We find that, up to\n$\\ell_{max}$=4000, baryonic physics plays very little role in the cosmological\nparameters estimation. However, if one goes up to $\\ell_{max}$=8000, the\nmarginalized errors on the cosmological parameters can be significantly\nreduced, but neglecting baryonic physics can lead to bias in the recovered\ncosmological parameters up to 10$\\sigma$. These biases are removed if one takes\ninto account the main baryonic parameter, $M_{\\rm crit}$, which can also be\ndetermined up to 1-2\\%, along with the other cosmological parameters.", "category": "astro-ph_CO" }, { "text": "Galaxy And Mass Assembly (GAMA): Spectroscopic analysis: The Galaxy And Mass Assembly (GAMA) survey is a multiwavelength photometric\nand spectroscopic survey, using the AAOmega spectrograph on the\nAnglo-Australian Telescope to obtain spectra for up to ~300000 galaxies over\n280 square degrees, to a limiting magnitude of r_pet < 19.8 mag. The target\ngalaxies are distributed over 00$. On the other\nhand, the criteria for radial stability is the same as in thick diks, i.e. that\nthe epicyclic frequency is positive.", "category": "astro-ph_CO" }, { "text": "Testing Gravity Using Large-Scale Redshift-Space Distortions: We use Luminous Red Galaxies from the Sloan Digital Sky Survey II to test the\ncosmological structure growth in two alternatives to the standard LCDM+GR\ncosmological model. We compare observed three-dimensional clustering in SDSS\nDR7 with theoretical predictions for the standard vanilla LCDM+GR model,\nUnified Dark Matter cosmologies and the normal branch DGP. In computing the\nexpected correlations in UDM cosmologies, we derive a parameterized formula for\nthe growth factor in these models. For our analysis we apply the methodology\ntested in Raccanelli et al. 2010 and use the measurements of Samushia et al.\n2011, that account for survey geometry, non-linear and wide-angle effects and\nthe distribution of pair orientation. We show that the estimate of the growth\nrate is potentially degenerate with wide-angle effects, meaning that extremely\naccurate measurements of the growth rate on large scales will need to take such\neffects into account. We use measurements of the zeroth and second order\nmoments of the correlation function from SDSS DR7 data and the Large Suite of\nDark Matter Simulations, and perform a likelihood analysis to constrain the\nparameters of the models. Using information on the clustering up to r_max = 120\nMpc/h, and after marginalizing over the bias, we find, for UDM models, a speed\nof sound < 6.1e-4, and, for the nDGP model, a cross-over scale r_c > 340 Mpc,\nat 95% confidence level.", "category": "astro-ph_CO" }, { "text": "Intrinsic colors and ages of extremely red elliptical galaxies at high\n redshift: In order to know the formation epoch of the oldest elliptical galaxies as a\nfunction of mass and observed redshift, a statistical analysis for 333\nextremely red objects (EROs) classified as old galaxies (OGs) at 0.8 0) or suppress (f_NL < 0) the\nprobability of giant-arc formation. Using the best value and 95% confidence\nlevels currently available from the Wilkinson Microwave Anisotropy Probe, we\nfind that the giant-arc optical depth for sources at z_s~2 is enhanced by ~20%\nand ~45% for f_NL = 32 and 74 respectively. In contrast, we calculate a\nsuppression of ~5% for f_NL = -10. These differences translate to similar\nrelative changes in the predicted all-sky number of giant arcs.", "category": "astro-ph_CO" }, { "text": "The role of Pop III stars and early black holes in the 21cm signal from\n Cosmic Dawn: Modeling the 21cm global signal from the Cosmic Dawn is challenging due to\nthe many poorly constrained physical processes that come into play. We address\nthis problem using the semi-analytical code \"Cosmic Archaeology Tool\" (CAT).\nCAT follows the evolution of dark matter halos tracking their merger history\nand provides an ab initio description of their baryonic evolution, starting\nfrom the formation of the first (Pop III) stars and black holes (BHs) in\nmini-halos at z > 20. The model is anchored to observations of galaxies and AGN\nat z < 6 and predicts a reionization history consistent with constraints. In\nthis work we compute the evolution of the mean global 21cm signal between\n$4\\leq z \\leq 40$ based on the rate of formation and emission properties of\nstars and accreting black holes. We obtain an absorption profile with a maximum\ndepth $\\delta {\\rm T_b} = -95$ mK at $z \\sim 26.5$ (54 MHz). This feature is\nquickly suppressed turning into an emission signal at $z = 20$ due to the\ncontribution of accreting BHs that efficiently heat the IGM at $z < 27$. The\nhigh-$z$ absorption feature is caused by the early coupling between the spin\nand kinetic temperature of the IGM induced by Pop III star formation episodes\nin mini-halos. Once we account for an additional radio background from early\nBHs, we are able to reproduce the timing and the depth of the EDGES signal only\nif we consider a smaller X-ray background from accreting BHs, but not the\nshape.", "category": "astro-ph_CO" }, { "text": "Causality, initial conditions, and inflationary magnetogenesis: The post-inflationary evolution of inflation-produced magnetic fields,\nconventional or not, can change dramatically when two fundamental issues are\naccounted for. The first is causality, which demands that local physical\nprocesses can never affect superhorizon perturbations. The second is the nature\nof the transition from inflation to reheating and then to the radiation era,\nwhich determine the initial conditions at the start of these epochs. Causality\nimplies that inflationary magnetic fields dot not freeze into the matter until\nthey have re-entered the causal horizon. The nature of the cosmological\ntransitions and the associated initial conditions, on the other hand, determine\nthe large-scale magnetic evolution after inflation. Put together, the two can\nslow down the adiabatic magnetic decay on superhorizon scales throughout the\nuniverse's post-inflationary evolution and thus lead to considerably stronger\nresidual magnetic fields. This is \"good news\" for both the conventional and the\nnon-conventional scenarios of cosmic magnetogenesis. Mechanisms operating\noutside standard electromagnetism, in particular, do not need to enhance their\nfields too much during inflation, in order to produce seeds that can feed the\ngalactic dynamo today. In fact, even conventionally produced inflationary\nmagnetic fields might be able to sustain the dynamo.", "category": "astro-ph_CO" }, { "text": "Testing Dvali-Gabadadze-Porrati Gravity with Planck: Recently, the Planck collaboration has released the first cosmological papers\nproviding the highest resolution, full sky, maps of the cosmic microwave\nbackground (CMB) temperature anisotropies. In this paper we study a\nphenomenological model which interpolates between the pure $\\Lambda$CDM model\nand the Dvali-Gabadadze-Porrati (DGP) braneworld model with an additional\nparameter $\\alpha$. Firstly, we calculate the \"distance information\" of Planck\ndata which includes the \"shift parameter\" $R$, the \"acoustic scale\" $l_A$, and\nthe photon decoupling epoch $z_\\ast$ in different cosmological models and find\nthat this information is almost independent on the input models we use. Then,\nwe compare the constraints on the free parameter $\\alpha$ of the DGP model from\nthe \"distance information\" of Planck and WMAP data and find that the Planck\ndata with high precision do not improve the constraint on $\\alpha$, but give\nthe higher median value and the better limit on the current matter density\nfraction $\\Omega_m$. Then, combining the \"distance information\" of Planck\nmeasurement, baryon acoustic oscillations (BAO), type Ia supernovae (SNIa) and\nthe prior on the current Hubble constant (HST), we obtain the tight constraint\non the parameter $\\alpha < 0.20$ at $95\\%$ confidence level, which implies that\nthe flat DGP model has been ruled out by the current cosmological data.\nFinally, we allow the additional parameter $\\alpha < 0$ in our calculations and\ninterestingly obtain $\\alpha=-0.29\\pm0.20$ ($68\\%$ C.L.), which means the\ncurrent data slightly favor the effective equation of state $w_{\\rm eff}<-1$.\nMore importantly, the tension between constraints on $H_0$ from different\nobservational data has been eased.", "category": "astro-ph_CO" }, { "text": "Confronting Models of Dwarf Galaxy Quenching with Observations of the\n Local Group: A number of mechanisms have been proposed to connect star-forming dwarf\nirregular galaxies with the formation of non-star-forming dwarf spheroidal\ngalaxies, but distinguishing between these mechanisms has been difficult. We\nuse the Via Lactea dark matter only cosmological simulations to test two\nwell-motivated simple hypotheses---transformation of irregulars into dwarf\nspheroidal galaxies by tidal stirring and ram pressure stripping following a\nclose passage to the host galaxy, and transformation via mergers between\ndwarfs---and predict the radial distribution and inferred formation times of\nthe resulting dwarf spheroidal galaxies. We compare this to the observed\ndistribution in the Local Group and show that 1) the observed dSph distribution\nfar from the Galaxy or M31 can be matched by the VL halos that have passed near\nthe host galaxy at least once, though significant halo-to-halo scatter exists,\n2) models that require two or more pericenter passages for dSph-formation\ncannot account for the dSphs beyond 500 kpc such as Cetus and Tucana, and 3)\nmergers predict a flat radial distribution of dSphs and cannot account for the\nhigh dSph fraction near the Galaxy, but are not ruled out at large distances.\nThe models also suggest that for dSphs found today beyond 500 kpc, mergers tend\nto occur significantly earlier than dwarf--host encounters, thus leading to a\npotentially observable difference in stellar populations. We argue that tidal\ninteractions are sufficient to reproduce the observed distribution of dSphs if\nand only if a single pericenter passage is sufficient to form a dSph.", "category": "astro-ph_CO" }, { "text": "The Copernicus Complexio: a high-resolution view of the small-scale\n Universe: We introduce Copernicus Complexio (COCO), a high-resolution cosmological\nN-body simulation of structure formation in the $\\Lambda{\\rm CDM}{}$ model.\nCOCO follows an approximately spherical region of radius $\\sim 17.4h^{-1}\\,{\\rm\nMpc}$ embedded in a much larger periodic cube that is followed at lower\nresolution. The high resolution volume has a particle mass of\n$1.135\\times10^5h^{-1}{\\rm M}_{\\odot}$ (60 times higher than the Millennium-II\nsimulation). COCO gives the dark matter halo mass function over eight orders of\nmagnitude in halo mass; it forms $\\sim 60$ haloes of galactic size, each\nresolved with about 10 million particles. We confirm the power-law character of\nthe subhalo mass function, $\\bar{N}(>\\mu)\\propto\\mu^{-s}$, down to a reduced\nsubhalo mass $M_{sub}/M_{200}\\equiv\\mu=10^{-6}$, with a best-fit power-law\nindex, $s=0.94$, for hosts of mass $\\langle M_{200}\\rangle=10^{12}h^{-1}{\\rm\nM}_{\\odot}$. The concentration-mass relation of COCO haloes deviates from a\nsingle power law for masses $M_{200}<\\textrm{a few}\\times 10^{8}h^{-1}{\\rm\nM}_{\\odot}$, where it flattens, in agreement with results by Sanchez-Conde et\nal. The host mass invariance of the reduced maximum circular velocity function\nof subhaloes, $\\nu\\equiv V_{max}/V_{200}$, hinted at in previous simulations,\nis clearly demonstrated over five orders of magnitude in host mass. Similarly,\nwe find that the average, normalised radial distribution of subhaloes is\napproximately universal (i.e. independent of subhalo mass), as previously\nsuggested by the Aquarius simulations of individual haloes. Finally, we find\nthat at fixed physical subhalo size, subhaloes in lower mass hosts typically\nhave lower central densities than those in higher mass hosts.", "category": "astro-ph_CO" }, { "text": "KiDS-450: Cosmological Constraints from Weak Lensing Peak Statistics -\n II: Inference from Shear Peaks using N-body Simulations: We study the statistics of peaks in a weak lensing reconstructed mass map of\nthe first 450 square degrees of the Kilo Degree Survey. The map is computed\nwith aperture masses directly applied to the shear field with an NFW-like\ncompensated filter. We compare the peak statistics in the observations with\nthat of simulations for various cosmologies to constrain the cosmological\nparameter $S_8 = \\sigma_8 \\sqrt{\\Omega_{\\rm m}/0.3}$, which probes the\n($\\Omega_{\\rm m}, \\sigma_8$) plane perpendicularly to its main degeneracy. We\nestimate $S_8=0.750\\pm0.059$, using peaks in the signal-to-noise range $0 \\leq\n{\\rm S/N} \\leq 4$, and accounting for various systematics, such as\nmultiplicative shear bias, mean redshift bias, baryon feedback, intrinsic\nalignment, and shear-position coupling. These constraints are $\\sim25\\%$\ntighter than the constraints from the high significance peaks alone ($3 \\leq\n{\\rm S/N} \\leq 4$) which typically trace single-massive halos. This\ndemonstrates the gain of information from low-S/N peaks. However we find that\nincluding ${\\rm S/N} < 0$ peaks does not add further information. Our results\nare in good agreement with the tomographic shear two-point correlation function\nmeasurement in KiDS-450. Combining shear peaks with non-tomographic\nmeasurements of the shear two-point correlation functions yields a $\\sim20\\%$\nimprovement in the uncertainty on $S_8$ compared to the shear two-point\ncorrelation functions alone, highlighting the great potential of peaks as a\ncosmological probe.", "category": "astro-ph_CO" }, { "text": "Curvature Perturbations Protected Against One Loop: We examine one-loop corrections from small-scale curvature perturbations to\nthe superhorizon-limit ones in single-field inflation models, which have\nrecently caused controversy. We consider the case where the Universe\nexperiences transitions of slow-roll (SR) $\\to$ intermediate period $\\to$ SR.\nThe intermediate period can be an ultra-slow-roll period or a resonant\namplification period, either of which enhances small-scale curvature\nperturbations. We assume that the superhorizon curvature perturbations are\nconserved at least during each of the SR periods. Within this framework, we\nshow that the superhorizon curvature perturbations during the first and the\nsecond SR periods coincide at one-loop level in the slow-roll limit.", "category": "astro-ph_CO" }, { "text": "The extraordinary mid-infrared spectral properties of FeLoBAL Quasars: We present mid-infrared spectra of six FeLoBAL QSOs at 1 r_c ~ 150\nMpc/h (i.e., no structures of size larger than r_c). Whether or not the\nobserved galaxy distribution is interpreted to be compatible with these\npredictions depend on the a-priori assumptions encoded in the statistical\nmethods employed to characterize the data and on the a-posteriori hypotheses\nmade to interpret the results. We present strategies to test the most common\nassumptions and we find evidences that, in the available samples, galaxy\ndistribution is spatially inhomogeneous for r<100 Mpc/h but statistically\nhomogeneous and isotropic. We conclude that the observed inhomogeneities pose a\nfundamental challenge to the standard picture of cosmology but they also\nrepresent an important opportunity which may open new directions for many\ncosmological puzzles.", "category": "astro-ph_CO" }, { "text": "A survey of molecular gas in luminous sub-millimetre galaxies: We present the results from a survey for 12CO emission in 40 luminous\nsub-millimetre galaxies (SMGs), with 850um fluxes of S850 = 4 - 20 mJy,\nconducted with the Plateau de Bure Interferometer. We detect 12CO emission in\n32 SMGs at z~1.2 - 4.1, including 16 SMGs not previously published. Using\nmultiple 12CO line (J_up =2 - 7) observations, we derive a median spectral line\nenergy distribution for luminous SMGs and use this to estimate a mean gas mass\nof (5.3 +/- 1.0) \\times 10^10 Msun. We report the discovery of a fundamental\nrelationship between 12CO FWHM and 12CO line luminosity in high-redshift\nstarbursts, which we interpret as a natural consequence of the baryon-dominated\ndynamics within the regions probed by our observations. We use far-infrared\nluminosities to assess the star-formation efficiency in our SMGs, finding a\nsteepening of the L'CO-LFIR relation as a function of increasing 12CO J_up\ntransition. We derive dynamical masses and molecular gas masses, and use these\nto determine the redshift evolution of the gas content of SMGs, finding that\nthey do not appear to be significantly more gas rich than less vigorously\nstar-forming galaxies at high redshifts. Finally, we collate X-ray\nobservations, and study the interdependence of gas and dynamical properties of\nSMGs with their AGN activity and supermassive black hole masses (MBH), finding\nthat SMGs lie significantly below the local M_BH-sigma relation. We conclude\nthat SMGs represent a class of massive, gas-rich ultraluminous galaxies with\nsomewhat heterogeneous properties, ranging from starbursting disc-like systems\nwith L~10^12 L_sun, to the most highly star-forming mergers in the Universe.", "category": "astro-ph_CO" }, { "text": "Massive and Newly Dead: Discovery of a Significant Population of\n Galaxies with High Velocity Dispersions and Strong Balmer Lines at z~1.5 from\n Deep Keck Spectra and HST/WFC3 Imaging: We present deep Keck/LRIS spectroscopy and HST/WFC3 imaging in the rest-frame\noptical for a sample of eight galaxies at z~1.5 with high\nphotometrically-determined stellar masses. The data are combined with\nVLT/XShooter spectra of five galaxies from van de Sande et al. (2011, 2012 to\nbe submitted). We find that these thirteen galaxies have high velocity\ndispersions, with a median of sigma=301 km s^{-1}. This high value is\nconsistent with their relatively high stellar masses and compact sizes. We\nstudy their stellar populations using the strength of Balmer absorption lines,\nwhich are not sensitive to dust absorption. We find a large range in Balmer\nabsorption strength, with many galaxies showing very strong lines indicating\nyoung ages. The median Hdelta_A equivalent width, determined directly or\ninferred from the H10 line, is 5.4 Angstroms, indicating a luminosity-weighted\nage of ~1 Gyr. Although this value may be biased towards higher values because\nof selection effects,high-dispersion galaxies with such young ages are\nextremely rare in the local Universe. Interestingly we do not find a simple\ncorrelation with rest-frame U-V color: some of the reddest galaxies have very\nstrong Balmer absorption lines. These results demonstrate that many\nhigh-dispersion galaxies at z~1.5 were quenched recently. This implies that\nthere must be a population of star-forming progenitors at z~2 with high\nvelocity dispersions or linewidths, which are notoriously absent from CO/Halpha\nselected surveys.", "category": "astro-ph_CO" }, { "text": "Multiphase Signatures of AGN Feedback in Abell 2597: We present new Chandra X-ray observations of the brightest cluster galaxy\n(BCG) in the cool core cluster Abell 2597. The data reveal an extensive\nkpc-scale X-ray cavity network as well as a 15 kpc filament of soft-excess gas\nexhibiting strong spatial correlation with archival VLA radio data. In addition\nto several possible scenarios, multiwavelength evidence may suggest that the\nfilament is associated with multiphase (10^3 - 10^7 K) gas that has been\nentrained and dredged-up by the propagating radio source. Stemming from a full\nspectral analysis, we also present profiles and 2D spectral maps of modeled\nX-ray temperature, entropy, pressure, and metal abundance. The maps reveal an\narc of hot gas which in projection borders the inner edge of a large X-ray\ncavity. Although limited by strong caveats, we suggest that the hot arc may be\n(a) due to a compressed rim of cold gas pushed outward by the radio bubble or\n(b) morphologically and energetically consistent with cavity-driven active\ngalactic nucleus (AGN) heating models invoked to quench cooling flows, in which\nthe enthalpy of a buoyant X-ray cavity is locally thermalized as ambient gas\nrushes to refill its wake. If confirmed, this would be the first observational\nevidence for this model.", "category": "astro-ph_CO" }, { "text": "Virial halo mass function in the ${\\it Planck}$ cosmology: We study halo mass functions with high-resolution $N$-body simulations under\na $\\Lambda$CDM cosmology. Our simulations adopt the cosmological model that is\nconsistent with recent measurements of the cosmic microwave backgrounds with\nthe ${\\it Planck}$ satellite. We calibrate the halo mass functions for\n$10^{8.5} \\lower.5ex\\hbox{$\\; \\buildrel < \\over \\sim \\;$} M_\\mathrm{vir} /\n(h^{-1}M_\\odot) \\lower.5ex\\hbox{$\\; \\buildrel < \\over \\sim \\;$} 10^{15.0 - 0.45\n\\, z}$, where $M_\\mathrm{vir}$ is the virial spherical overdensity mass and\nredshift $z$ ranges from $0$ to $7$. The halo mass function in our simulations\ncan be fitted by a four-parameter model over a wide range of halo masses and\nredshifts, while we require some redshift evolution of the fitting parameters.\nOur new fitting formula of the mass function has a 5\\%-level precision except\nfor the highest masses at $z\\le 7$. Our model predicts that the analytic\nprediction in Sheth $\\&$ Tormen would overestimate the halo abundance at $z=6$\nwith $M_\\mathrm{vir} = 10^{8.5-10}\\, h^{-1}M_\\odot$ by $20-30\\%$. Our\ncalibrated halo mass function provides a baseline model to constrain warm dark\nmatter (WDM) by high-$z$ galaxy number counts. We compare a cumulative\nluminosity function of galaxies at $z=6$ with the total halo abundance based on\nour model and a recently proposed WDM correction. We find that WDM with its\nmass lighter than $2.71\\, \\mathrm{keV}$ is incompatible with the observed\ngalaxy number density at a $2\\sigma$ confidence level.", "category": "astro-ph_CO" }, { "text": "A New Probe of the High-z BAO scale: BAO tomography With CMB $\\times$\n LIM-Nulling Convergence: Standard rulers such as the baryon acoustic oscillation (BAO) scale serve as\nworkhorses for precision tests of cosmology, enabling distance measurements\nthat probe the geometry and expansion history of our Universe. Aside from BAO\nmeasurements from the cosmic microwave background (CMB), most standard ruler\ntechniques operate at relatively low redshifts and depend on biased tracers of\nthe matter density field. In a companion paper, we explored the scientific\nreach of nulling estimators, where CMB lensing convergence maps are\ncross-correlated with linear combinations of similar maps from line intensity\nmapping (LIM) to precisely null out the low-redshift contributions to CMB\nlensing. We showed that nulling estimators can be used to constrain the high\nredshift matter power spectrum and showed that this spectrum exhibits\ndiscernible BAO features. Here we propose using these features as a standard\nruler at high redshifts that does not rely on biased tracers. Forecasting such\na measurement at $z \\sim 5$, we find that next-generation instruments will be\nable to constrain the BAO scale to percent-level precision at $7.2 \\%$, while\nour futuristic observing scenario can constrain the BAO scale to $4\\%$\nprecision. This constitutes a fundamentally new kind of BAO measurement during\nearly epochs in our cosmic history.", "category": "astro-ph_CO" }, { "text": "The Trispectrum in the Effective Theory of Inflation with Galilean\n symmetry: We calculate the trispectrum of curvature perturbations for a model of\ninflation endowed with Galilean symmetry at the level of the fluctuations\naround an FRW background. Such a model has been shown to posses desirable\nproperties such as unitarity (up to a certain scale) and non-renormalization of\nthe leading operators, all of which point towards the reasonable assumption\nthat a full theory whose fluctuations reproduce the one here might exist as\nwell as be stable and predictive. The cubic curvature fluctuations of this\nmodel produce quite distinct signatures at the level of the bispectrum. Our\nanalysis shows how this holds true at higher order in perturbations. We provide\na detailed study of the trispectrum shape-functions in different configurations\nand a comparison with existent literature. Most notably, predictions markedly\ndiffer from their P(X,\\phi) counterpart in the so called equilateral\ntrispectrum configuration. The zoo of inflationary models characterized by\nsomewhat distinctive predictions for higher order correlators is already quite\npopulated; what makes this model more compelling resides in the above mentioned\nstability properties.", "category": "astro-ph_CO" }, { "text": "Bridging the gap: spectral distortions meet gravitational waves: Gravitational waves (GWs) have the potential to probe the entirety of\ncosmological history due to their nearly perfect decoupling from the thermal\nbath and any intervening matter after emission. In recent years, GW cosmology\nhas evolved from merely being an exciting prospect to an actively pursued\navenue for discovery, and the early results are very promising. As we highlight\nin this paper, spectral distortions (SDs) of the cosmic microwave background\n(CMB) uniquely probe GWs over six decades in frequency, bridging the gap\nbetween astrophysical high- and cosmological low-frequency measurements. This\nmeans SDs will not only complement other GW observations, but will be the sole\nprobe of physical processes at certain scales. To illustrate this point, we\nexplore the constraining power of various proposed SD missions on a number of\nphenomenological scenarios: early-universe phase transitions (PTs), GW\nproduction via the dynamics of SU(2) and ultra-light U(1) axions, and cosmic\nstring (CS) network collapse. We highlight how some regions of parameter space\nwere already excluded with data from COBE/FIRAS, taken over two decades ago. To\nfacilitate the implementation of SD constraints in arbitrary models we provide\nGW2SD. This tool calculates the window function, which easily maps a GW\nspectrum to a SD amplitude, thus opening another portal for GW cosmology with\nSDs, with wide reaching implications for particle physics phenomenology.", "category": "astro-ph_CO" }, { "text": "Accurate AGN black hole masses and the scatter in the M_{bh} - L_{bulge}\n relationship: A new empirical formulae is given for estimating the masses of black holes in\nAGNs from the H beta velocity dispersion and the continuum luminosity at 5100\nAngstroms. It is calibrated to reverberation-mapping and stellar-dynamical\nestimates of black hole masses. The resulting mass estimates are as accurate as\nreverberation-mapping and stellar-dynamical estimates. The new mass estimates\nshow that there is very little scatter in the M_{bh} - L_{bulge} relationship\nfor high-luminosity galaxies, and that the scatter increases substantially in\nlower-mass galaxies.", "category": "astro-ph_CO" }, { "text": "H0LiCOW I. $H_0$ Lenses in COSMOGRAIL's Wellspring: Program Overview: Strong gravitational lens systems with time delays between the multiple\nimages allow measurements of time-delay distances, which are primarily\nsensitive to the Hubble constant that is key to probing dark energy, neutrino\nphysics, and the spatial curvature of the Universe, as well as discovering new\nphysics. We present H0LiCOW ($H_0$ Lenses in COSMOGRAIL's Wellspring), a\nprogram that aims to measure $H_0$ with $<3.5\\%$ uncertainty from five lens\nsystems (B1608+656, RXJ1131-1231, HE0435-1223, WFI2033-4723 and HE1104-1805).\nWe have been acquiring (1) time delays through COSMOGRAIL and Very Large Array\nmonitoring, (2) high-resolution Hubble Space Telescope imaging for the lens\nmass modeling, (3) wide-field imaging and spectroscopy to characterize the lens\nenvironment, and (4) moderate-resolution spectroscopy to obtain the stellar\nvelocity dispersion of the lenses for mass modeling. In cosmological models\nwith one-parameter extension to flat $\\Lambda$CDM, we expect to measure $H_0$\nto $<3.5\\%$ in most models, spatial curvature $\\Omega_{\\rm k}$ to 0.004, $w$ to\n0.14, and the effective number of neutrino species to 0.2 (1$\\sigma$\nuncertainties) when combined with current CMB experiments. These are,\nrespectively, a factor of $\\sim15$, $\\sim2$, and $\\sim1.5$ tighter than CMB\nalone. Our data set will further enable us to study the stellar initial mass\nfunction of the lens galaxies, and the co-evolution of supermassive black holes\nand their host galaxies. This program will provide a foundation for extracting\ncosmological distances from the hundreds of time-delay lenses that are expected\nto be discovered in current and future surveys.", "category": "astro-ph_CO" }, { "text": "The effect of massive neutrinos on the BAO peak: We study the impact of neutrino masses on the shape and height of the BAO\npeak of the matter correlation function, both in real and redshift space. In\norder to describe the nonlinear evolution of the BAO peak we run N-body\nsimulations and compare them with simple analytic formulae. We show that the\nevolution with redshift of the correlation function and its dependence on the\nneutrino masses is well reproduced in a simplified version of the Zel'dovich\napproximation, in which the mode-coupling contribution to the power spectrum is\nneglected. While in linear theory the BAO peak decreases for increasing\nneutrino masses, the effect of nonlinear structure formation goes in the\nopposite direction, since the peak broadening by large scale flows is less\neffective. As a result of this combined effect, the peak decreases by $\\sim 0.6\n\\%$ for $ \\sum m_\\nu = 0.15$ eV and increases by $\\sim1.2 \\%$ for $ \\sum m_\\nu\n= 0.3$ eV, with respect to a massless neutrino cosmology with equal value of\nthe other cosmological parameters. We extend our analysis to redshift space and\nto halos, and confirm the agreement between simulations and the analytic\nformulae. We argue that all analytical approaches having the Zel'dovich\npropagator in their lowest order approximation should give comparable\nperformances, irrespectively to their formulation in Lagrangian or in Eulerian\nspace.", "category": "astro-ph_CO" }, { "text": "Intrinsic brightness of SDSS objects is similar at all redshifts in de\n Sitter space: The redshift-luminosity distributions for well-defined galaxies and quasars\nin the Sloan Digital Sky Survey (SDSS) are compared for the two\nredshift-distance relations of a Hubble redshift and a de Sitter redshift.\nAssuming a Hubble redshift, SDSS data can be interpreted as luminosity\nevolution following the Big Bang. In contrast, given a de Sitter redshift, the\nintrinsic brightness of objects at all redshifts is roughly the same. In a de\nSitter universe, 95 per cent of SDSS galaxies and quasars fall into a magnitude\nrange of only 2.8, and 99.7 per cent are within 5.4 mag. The comparable Hubble\nluminosity ranges are much larger: 95 per cent within 6.9, and 99.7 per cent\nwithin 11.5 mag. De Sitter space is now widely discussed, but the de Sitter\nredshift is hardly mentioned.", "category": "astro-ph_CO" }, { "text": "Observational constraints on the tilted spatially-flat and the untilted\n nonflat $\u03c6$CDM dynamical dark energy inflation models: We constrain spatially-flat tilted and nonflat untilted scalar field ($\\phi$)\ndynamical dark energy inflation ($\\phi$CDM) models by using Planck 2015 cosmic\nmicrowave background (CMB) anisotropy measurements and recent baryonic acoustic\noscillation distance observations, Type Ia supernovae apparent magnitude data,\nHubble parameter measurements, and growth rate data. We assume an inverse\npower-law scalar field potential energy density $V(\\phi)=V_0 \\phi^{-\\alpha}$.\nWe find that the combination of the CMB data with the four non-CMB data sets\nsignificantly improves parameter constraints and strengthens the evidence for\nnonflatness in the nonflat untilted $\\phi$CDM case from $1.8\\sigma$ for the CMB\nmeasurements only to more than $3.1\\sigma$ for the combined data. In the\nnonflat untilted $\\phi$CDM model current observations favor a spatially closed\nuniverse with spatial curvature contributing about two-thirds of a percent of\nthe present cosmological energy budget. The flat tilted $\\phi$CDM model is a\n0.4$\\sigma$ better fit to the data than is the standard flat tilted\n$\\Lambda$CDM model: current data allow for the possibility that dark energy is\ndynamical. The nonflat tilted $\\phi$CDM model is in better accord with the Dark\nEnergy Survey bounds on the rms amplitude of mass fluctuations now ($\\sigma_8$)\nas a function of the nonrelativistic matter density parameter now ($\\Omega_m$)\nbut it does not provide as good a fit to the larger-multipole Planck 2015 CMB\nanisotropy data as does the standard flat tilted $\\Lambda$CDM model. A few\ncosmological parameter value measurements differ significantly when determined\nusing the tilted flat and the untilted nonflat $\\phi$CDM models, including the\ncold dark matter density parameter and the reionization optical depth.", "category": "astro-ph_CO" }, { "text": "Cosmic transparency and acceleration: In this paper, by considering an absorption probability independent of photon\nwavelength, we show that current type Ia supernovae (SNe Ia) and gamma ray\nburst (GRBs) observations plus high-redshift measurements of the cosmic\nmicrowave background (CMB) radiation temperature support cosmic acceleration\nregardless of the transparent-universe assumption. Two flat scenarios are\nconsidered in our analyses: the $\\Lambda$CDM model and a kinematic model. We\nconsider $\\tau(z)=2\\ln(1+z)^{\\varepsilon}$, where $\\tau(z)$ denotes the opacity\nbetween an observer at $z=0$ and a source at $z$. This choice is equivalent to\ndeforming the cosmic distance duality relation as $D_LD^{-1}_A = (1 +\nz)^{2+\\varepsilon}$ and, if the absorption probability is independent of photon\nwavelength, the CMB temperature evolution law is\n$T_{CMB}(z)=T_0(1+z)^{1+2\\varepsilon/3 }$. By marginalizing on the\n$\\varepsilon$ parameter, our analyses rule out a decelerating universe at 99.99\n\\% c.l. for all scenarios considered. Interestingly, by considering only SNe Ia\nand GRBs observations, we obtain that a decelerated universe indicated by\n$\\Omega_{\\Lambda} \\leq 0.33$ and $q_0 > 0$ is ruled out around 1.5$\\sigma$ c.l.\nand 2$\\sigma$ c.l., respectively, regardless of the transparent-universe\nassumption.", "category": "astro-ph_CO" }, { "text": "Swift BAT, Fermi LAT, and the Blazar Sequence: Using public \\fermi LAT and \\swift BAT observations, we constructed the first\nsample of blazars selected at both hard X-rays and gamma-rays. Studying its\nspectral properties, we find a luminosity dependence of the spectral slopes at\nboth energies. Specifically, luminous blazars, generally classified as FSRQs,\nhave {\\it hard} continua in the medium-hard X-ray range but {\\it soft} continua\nin the LAT gamma-ray range (photon indices $\\Gamma_X$ \\ltsima 2 and $\\Gamma_G$\n\\gtsima 2), while lower luminosity blazars, classified as BL Lacs, have\nopposite behavior, i.e., {\\it soft} X-ray and {\\it hard} gamma-ray continua\n($\\Gamma_X$ \\gtsima 2.4 and $\\Gamma_G < 2$). The trends are confirmed by\ndetailed Monte Carlo simulations explicitly taking into account the\nobservational biases of both instruments. Our results support the so-called\n``blazar sequence'' which was originally based on radio samples of blazars and\nradio luminosities. We also argue that the X-ray-to-gamma-ray continua of\nblazars may provide independent insights into the physical conditions around\nthe jet, complementing/superseding the ambiguities of the traditional\nclassification based on optical properties.", "category": "astro-ph_CO" }, { "text": "B-mode in CMB polarization. What's that and why it is interesting: Generation of the B-mode of CMB polarization by background of relic\ngravitational wave is discussed in connection with the BICEP2 measurements.\nDescription of the polarization maps in terms of the eigenvectors of the\npolarization matrix is considered.", "category": "astro-ph_CO" }, { "text": "Post-Planck Dark Energy Constraints: We constrain plausible dark energy models, parametrized by multiple candidate\nequation of state, using the recently published Cosmic Microwave Background\n(CMB) temperature anisotropy data from Planck together with the WMAP-9\nlow-$\\ell$ polarization data and data from low redshift surveys. To circumvent\nthe limitations of any particular equation of state towards describing all\nexisting dark energy models, we work with three different equation of state\ncovering a broader class of dark energy models and, hence, provide more robust\nand generic constraints on the dark energy properties. We show that a clear\ntension exists between dark energy constraints from CMB and non-CMB\nobservations when one allows for dark energy models having both phantom and\nnon-phantom behavior; while CMB is more favorable to phantom models, the low-z\ndata prefers model with behavior close to a Cosmological Constant. Further, we\nreconstruct the equation of state of dark energy as a function of redshift\nusing the results from combined CMB and non-CMB data and find that Cosmological\nConstant lies outside the 1$\\sigma$ band for multiple dark energy models\nallowing phantom behavior. A considerable fine tuning is needed to keep models\nwith strict non-phantom history inside 2$\\sigma$ allowed range. This result\nmight motivate one to construct phantom models of dark energy,which is\nachievable in the presence of higher derivative operators as in string theory.\nHowever, disallowing phantom behavior, based only on strong theoretical prior,\nleads to both CMB and non-CMB datasets agree on the nature of dark energy, with\nthe mean equation of state being very close to the Cosmological Constant.\nFinally, to illustrate the impact of additional dark energy parameters on other\ncosmological parameters, we provide the cosmological parameter constraints for\ndifferent dark energy models.", "category": "astro-ph_CO" }, { "text": "Gravitational waves, dark energy and inflation: In this paper we first present a complete classification of gravitational\nwaves according to their frequencies: (i) Ultra high frequency band (above 1\nTHz); (ii) Very high frequency band (100 kHz - 1 THz); (iii) High frequency\nband (10 Hz - 100 kHz); (iv) Middle frequency band (0.1 Hz - 10 Hz); (v) Low\nfrequency band (100 nHz - 0.1 Hz); (vi) Very low frequency band (300 pHz - 100\nnHz); (vii) Ultra low frequency band (10 fHz - 300 pHz); (viii) Hubble\n(extremely low) frequency band (1 aHz - 10 fHz); (ix) Infra-Hubble frequency\nband (below 1 aHz). After briefly discussing the method of detection for\ndifferent frequency bands, we review the concept and status of space\ngravitational-wave missions --- LISA, ASTROD, ASTROD-GW, Super-ASTROD, DECIGO\nand Big Bang Observer. We then address to the determination of dark energy\nequation, and probing the inflationary physics using space gravitational wave\ndetectors.", "category": "astro-ph_CO" }, { "text": "Testing flatness of the universe with probes of cosmic distances and\n growth: When using distance measurements to probe spatial curvature, the geometric\ndegeneracy between curvature and dark energy in the distance-redshift relation\ntypically requires either making strong assumptions about the dark energy\nevolution or sacrificing precision in a more model-independent approach.\nMeasurements of the redshift evolution of the linear growth of perturbations\ncan break the geometric degeneracy, providing curvature constraints that are\nboth precise and model-independent. Future supernova, CMB, and cluster data\nhave the potential to measure the curvature with an accuracy of\nsigma(Omega_K)=0.002, without specifying a particular dark energy\nphenomenology. In combination with distance measurements, the evolution of the\ngrowth function at low redshifts provides the strongest curvature constraint if\nthe high-redshift universe is well approximated as being purely matter\ndominated. However, in the presence of early dark energy or massive neutrinos,\nthe precision in curvature is reduced due to additional degeneracies, and\nprecise normalization of the growth function relative to recombination is\nimportant for obtaining accurate constraints. Curvature limits from distances\nand growth compare favorably to other approaches to curvature estimation\nproposed in the literature, providing either greater accuracy or greater\nfreedom from dark energy modeling assumptions, and are complementary due to the\nuse of independent data sets. Model-independent estimates of curvature are\ncritical for both testing inflation and obtaining unbiased constraints on dark\nenergy parameters.", "category": "astro-ph_CO" }, { "text": "Effects of a Late Gravitational Transition on Gravitational Waves and\n Anticipated Constraints: We investigate the evolution of gravitational waves through discontinuous\nevolution (transition) of the Hubble expansion rate $H(z)$ at a sudden\ncosmological singularity, which may be due to a transition of the value of the\ngravitational constant. We find the evolution of the scale factor and the\ngravitational wave waveform through the singularity by imposing the proper\nboundary conditions. We also use existing cosmological data and mock data of\nfuture gravitational wave experiments (the ET) to impose current and\nanticipated constraints on the magnitude of such a transition. We show that\nmock data of the Einstein Telescope can reduce the uncertainties by up to a\nfactor of three depending on the cosmological parameter considered.", "category": "astro-ph_CO" }, { "text": "Cosmic string loop shapes: We analyze the shapes of cosmic string loops found in large-scale simulations\nof an expanding-universe string network. The simulation does not include\ngravitational back reaction, but we model that process by smoothing the loop\nusing Lorentzian convolution. We find that loops at formation consist of\ngenerally straight segments separated by kinks. We do not see cusps or any\ncusp-like structure at the scale of the entire loop, although we do see very\nsmall regions of string that move with large Lorentz boosts. However, smoothing\nof the string almost always introduces two cusps on each loop. The smoothing\nprocess does not lead to any significant fragmentation of loops that were in\nnon-self-intersecting trajectories before smoothing.", "category": "astro-ph_CO" }, { "text": "The sub-mJy radio population of the E-CDFS: optical and infrared\n counterpart identification: We study a sample of 883 sources detected in a deep Very Large Array survey\nat 1.4 GHz in the Extended Chandra Deep Field South. The paper focuses on the\nidentification of their optical and infrared (IR) counterparts. We use a\nlikelihood ratio technique that is particularly useful when dealing with deep\noptical images to minimize the number of spurious associations. We find a\nreliable counterpart for 95% of our radio sources. Most of the counterparts\n(74%) are detected at optical wavelengths, but there is a significant fraction\n(21%) only detectable in the IR. Combining newly acquired optical spectra with\ndata from the literature we are able to assign a redshift to 81% of the\nidentified radio sources (37% spectroscopic). We also investigate the X-ray\nproperties of the radio sources using the Chandra 4 Ms and 250 ks observations.\nIn particular, we use a stacking technique to derive the average properties of\nradio objects undetected in the Chandra images. The results of our analysis are\ncollected in a new catalog containing the position of the optical/IR\ncounterpart, the redshift information and the X-ray fluxes. It is the deepest\nmulti-wavelength catalog of radio sources, which will be used for future study\nof this galaxy population.", "category": "astro-ph_CO" }, { "text": "Calibrated Ultra Fast Image Simulations for the Dark Energy Survey: Weak lensing by large-scale structure is a powerful technique to probe the\ndark components of the universe. To understand the measurement process of weak\nlensing and the associated systematic effects, image simulations are becoming\nincreasingly important. For this purpose we present a first implementation of\nthe $\\textit{Monte Carlo Control Loops}$ ($\\textit{MCCL}$; Refregier & Amara\n2014), a coherent framework for studying systematic effects in weak lensing. It\nallows us to model and calibrate the shear measurement process using image\nsimulations from the Ultra Fast Image Generator (UFig; Berge et al. 2013). We\napply this framework to a subset of the data taken during the Science\nVerification period (SV) of the Dark Energy Survey (DES). We calibrate the UFig\nsimulations to be statistically consistent with DES images. We then perform\ntolerance analyses by perturbing the simulation parameters and study their\nimpact on the shear measurement at the one-point level. This allows us to\ndetermine the relative importance of different input parameters to the\nsimulations. For spatially constant systematic errors and six simulation\nparameters, the calibration of the simulation reaches the weak lensing\nprecision needed for the DES SV survey area. Furthermore, we find a sensitivity\nof the shear measurement to the intrinsic ellipticity distribution, and an\ninterplay between the magnitude-size and the pixel value diagnostics in\nconstraining the noise model. This work is the first application of the\n$\\textit{MCCL}$ framework to data and shows how it can be used to methodically\nstudy the impact of systematics on the cosmic shear measurement.", "category": "astro-ph_CO" }, { "text": "Metals and ionizing photons from dwarf galaxies: We estimate the potential contribution of M < 10^9 Msun dwarf galaxies to the\nreionization and early metal-enrichment of the Milky Way environment, or\ncircum-Galactic Medium. Our approach is to use the observed properties of\nancient stars (> 12 Gyr old) measured in nearby dwarf galaxies to characterize\nthe star-formation at high-z. We use a merger-tree model for the build-up of\nthe Milky Way, which self-consistently accounts for feedback processes, and\nwhich is calibrated to match the present-day properties of the Galaxy and its\ndwarf satellites. We show that the high-z analogues of nearby dwarf galaxies\ncan produce the bulk of ionizing radiation (>80%) required to reionize the\nMilky Way environment. Our fiducial model shows that the gaseous environment\ncan be 50% reionized at z ~ 8 by galaxies with 10^7 Msun < M < 10^8 Msun. At\nlater times, radiative feedback stops the star-formation in these small\nsystems, and reionization is completed by more massive dwarf galaxies by z_rei\n= 6.4\\pm 0.5. The metals ejected by supernova-driven outflows from M < 10^9\nMsun dwarf galaxies almost uniformly fill the Milky Way environment by z ~ 5,\nenriching it to Z ~ 2 10^-2 Zsun. At z ~ 2 these early metals are still found\nto represent ~ 50% of the total mass of heavy elements in the circum-Galactic\nMedium.", "category": "astro-ph_CO" }, { "text": "The Evolution and Eddington Ratio Distribution of Compton Thick Active\n Galactic Nuclei: Previous studies of the active galactic nuclei (AGN) contribution to the\ncosmic X-ray background (CXB) consider only observable parameters such as\nluminosity and absorbing column. Here, for the first time, we extend the study\nof the CXB to physical parameters including the Eddington ratio of the sources\nand the black hole mass. In order to calculate the contribution to the CXB of\nAGN accreting at various Eddington ratios, an evolving Eddington ratio space\ndensity model is calculated. In particular, Compton thick (CT) AGN are modeled\nas accreting at specific, physically motivated Eddington ratios instead of as a\nsimple extension of the Compton thin type 2 AGN population. Comparing against\nthe observed CT AGN space densities and log N-log S relation indicates that CT\nAGN are likely a composite population of AGN made up of sources accreting\neither at >90% or <1% of their Eddington rate.", "category": "astro-ph_CO" }, { "text": "Environmental Effects on the Star Formation Activity in Galaxies at\n z=1.2 in the COSMOS Field: We investigate the relation between the star-formation activity in galaxies\nand environment at z=1.2 in the COSMOS field, using the fraction of [OII]\nemitters and the local galaxy density. The fraction of [OII] emitters appears\nto be almost constant over the surface density of galaxies between 0.2 and 10\nMpc^-2. This trend is different from that seen in the local universe where the\nstar-formation activity is weaker in higher density regions. To understand this\ndifference between z~1 and z~0, we study the fraction of non-isolated galaxies\nas a function of local galaxy density. We find that the fraction of\nnon-isolated galaxies increases with increasing density. Our results suggest\nthat the star formation in galaxies at z~1 is triggered by galaxy interaction\nand/or mergers.", "category": "astro-ph_CO" }, { "text": "Light Fields during Inflation from BOSS and Future Galaxy Surveys: Primordial non-Gaussianity generated by additional fields present during\ninflation offers a compelling observational target for galaxy surveys. These\nfields are of significant theoretical interest since they offer a window into\nparticle physics in the inflaton sector. They also violate the single-field\nconsistency conditions and induce a scale-dependent bias in the galaxy power\nspectrum. In this paper, we explore this particular signal for light scalar\nfields and study the prospects for measuring it with galaxy surveys. We find\nthat the sensitivities of current and future surveys are remarkably stable for\ndifferent configurations, including between spectroscopic and photometric\nredshift measurements. This is even the case at non-zero masses where the\nsignal is not obviously localized on large scales. For realistic galaxy number\ndensities, we demonstrate that the redshift range and galaxy bias of the sample\nhave the largest impact on the sensitivity in the power spectrum. These results\nadditionally motivated us to explore the potentially enhanced sensitivity of\nVera Rubin Observatory's LSST through multi-tracer analyses. Finally, we apply\nthis understanding to current data from the last data release of the Baryon\nOscillation Spectroscopic Survey (BOSS DR12) and place new constraints on light\nfields coupled to the inflaton.", "category": "astro-ph_CO" }, { "text": "Multiband Comparative Study of Optical Microvariability in RL vs. RQ\n Quasars: We present the results of an optical multi-band (BVR) photometric monitoring\nprogram of 22 core-dominated radio-loud quasars (CRLQs) and 22 radio-quiet\nquasars (RQQs). The aim was to compare the properties of microvariability in\nboth types of quasars. We detected optical microvariability in 5 RQQs and 4\nCRLQs. Our results confirm that microvariability in RQQs may be as frequent as\nin CRLQs. In addition we compare microvariability duty cycles in different\nbands. Finally, the implications for the origin of the microvariations are\nbriefly discussed.", "category": "astro-ph_CO" }, { "text": "Connecting massive galaxies to dark matter halos in BOSS - I. Is galaxy\n color a stochastic process in high-mass halos?: We use subhalo abundance matching (SHAM) to model the stellar mass function\n(SMF) and clustering of the Baryon Oscillation Spectroscopic Survey (BOSS)\n\"CMASS\" sample at $z\\sim0.5$. We introduce a novel method which accounts for\nthe stellar mass incompleteness of CMASS as a function of redshift, and produce\nCMASS mock catalogs which include selection effects, reproduce the overall SMF,\nthe projected two-point correlation function $w_{\\rm p}$, the CMASS $dn/dz$,\nand are made publicly available. We study the effects of assembly bias above\ncollapse mass in the context of \"age matching\" and show that these effects are\nmarkedly different compared to the ones explored by Hearin et al. (2013) at\nlower stellar masses. We construct two models, one in which galaxy color is\nstochastic (\"AbM\" model) as well as a model which contains assembly bias\neffects (\"AgM\" model). By confronting the redshift dependent clustering of\nCMASS with the predictions from our model, we argue that that galaxy colors are\nnot a stochastic process in high-mass halos. Our results suggest that the\ncolors of galaxies in high-mass halos are determined by other halo properties\nbesides halo peak velocity and that assembly bias effects play an important\nrole in determining the clustering properties of this sample.", "category": "astro-ph_CO" }, { "text": "X-ray observations of the merging cluster CIZA J2242.8+5301: Multiwavelength studies of radio relics at merger shocks set powerful\nconstraints on the relics origin and formation mechanism. However, for X-ray\nobservations, a main difficulty is represented by the low X-ray surface\nbrightness far out in the cluster outskirts, where relics are typically found.\nHere, we present XMM-Newton results from a 130-ks observation of CIZA\nJ2242.8+5301, a cluster at z=0.19 that hosts a double radio relic. We focus on\nthe well-defined northern relic. There is a difference of ~55% between the\ntemperature we measure behind the relic, and the temperature measured with\nSuzaku. We analyse the reasons for this large discrepancy, and discuss the\npossibility of reliably measuring the temperature beyond the northern relic.", "category": "astro-ph_CO" }, { "text": "Detectability of the cross-correlation between CMB lensing and\n stochastic GW background from compact object mergers: The anisotropies of the Stochastic Gravitational-Wave Background (SGWB)\nproduced by merging compact binaries constitute a possible new probe of the\nLarge-Scale Structure (LSS). However, the significant shot noise contribution\ncaused by the discreteness of the GW sources and the poor angular resolution of\nthe instruments hamper the detection of the intrinsic anisotropies induced by\nthe LSS. In this work, we investigate the potential of cross-correlating\nforthcoming high precision measurements of the SGWB energy density and the\nCosmic Microwave Background (CMB) lensing convergence to mitigate the effect of\nshot noise. Combining a detailed model of stellar and galactic astrophysics\nwith a novel framework to distribute the GW emitters in the sky, we compute the\nauto- and cross-correlation power spectra for the two cosmic fields, evaluate\nthe shot noise contribution and predict the signal-to-noise ratio. The results\nof our analysis show that the SGWB energy density correlates significantly with\nthe CMB lensing convergence and that the cross-correlation between these two\ncosmic fields reduces the impact of instrumental and shot noise. Unfortunately,\nthe S/N is not high enough to detect the intrinsic SGWB anisotropies.\nNevertheless, a network composed of both present and future generation GW\ninterferometers, operating for at least 10 yrs, should be able to measure the\nshot noise contribution.", "category": "astro-ph_CO" }, { "text": "A unique isolated dwarf spheroidal galaxy at D=1.9 Mpc: We present a photometric and spectroscopic study of the unique isolated\nnearby dSph galaxy KKR25. The galaxy was resolved into stars with HST/WFPC2\nincluding old red giant branch and red clump. We have constructed a model of\nthe resolved stellar populations and measured the star formation rate and\nmetallicity as function of time. The main star formation activity period\noccurred about 12.6 to 13.7 Gyr ago. These stars are mostly metal-poor, with a\nmean metallicity [Fe/H]\\sim -1 to -1.6 dex. About 60 per cent of the total\nstellar mass was formed during this event. There are indications of\nintermediate age star formation in KKR25 between 1 and 4 Gyr with no\nsignificant signs of metal enrichment for these stars. Long-slit spectroscopy\nwas carried out using the Russian 6-m telescope of the integrated starlight and\nbright individual objects in the galaxy. We have discovered a planetary nebula\n(PN) in KKR25. This is the first known PN in a dwarf spheroidal galaxy outside\nthe Local Group. We have measured its oxygen abundance 12+log(O/H)=7.60+-0.07\ndex and a radial velocity Vh=-79 km/s. We have analysed the stellar density\ndistribution in the galaxy body. The galaxy has an exponential surface\nbrightness profile with a central light depression. We discuss the evolutionary\nstatus of KKR25, which belongs to a rare class of very isolated dwarf galaxies\nwith spheroidal morphology.", "category": "astro-ph_CO" }, { "text": "Cross-Correlation of Diffuse Synchrotron and Large-Scale Structures: We explore for the first time the method of cross-correlation of radio\nsynchrotron emission and tracers of large-scale structure in order to detect\nthe diffuse IGM/WHIM. We performed a cross-correlation of a 34 x 34 degree area\nof 2MASS galaxies for two redshift slices (0.03 < z < 0.04 and 0.06 < z < 0.07)\nwith the corresponding region of the 1.4 GHz Bonn survey. For this analysis, we\nassumed that the synchrotron surface brightness is linearly proportional to\nsurface density of galaxies. We also sampled the cross-correlation function\nusing 24 distant fields of the same size from the Bonn survey, to better assess\nthe noise properties. Though we obtained a null result, we found that by adding\na signal weighted by the 2MASS image with a filament (peak) surface brightness\nof 1 (7) mK and 7 (49) mK would produce a 3 sigma positive correlation for the\n0.03 < z < 0.04 and 0.06 < z < 0.07 redshift slices respectively. These\ndetection thresholds correspond to minimum energy magnetic fields as low as 0.2\nmicroG, close to some theoretical expectations for filament field values. This\ninjected signal is also below the rms noise of the Bonn survey, and\ndemonstrates the power of this technique and its utility for upcoming sensitive\ncontinuum surveys such as GALFACTS at Arecibo and those planned with the\nMurchison Widefield Array (MWA).", "category": "astro-ph_CO" }, { "text": "The Brightest of Reionizing Galaxies (BoRG) survey: Until now, investigating the early stages of galaxy formation has been\nprimarily the realm of theoretical modeling and computer simulations, which\nrequire many physical ingredients and are challenging to test observationally.\nHowever, the latest Hubble Space Telescope observations in the near infrared\nare shedding new light on the properties of galaxies within the first billion\nyears after the Big Bang, including our recent discovery of the most distant\nproto-cluster of galaxies at redshift z~8. Here, I compare predictions from\nmodels of primordial and metal-enriched star formation during the dark ages\nwith the latest Hubble observations of galaxies during the epoch of\nreionization. I focus in particular on the luminosity function and on galaxy\nclustering as measured from our Hubble Space Telescope Brightest of Reionizing\nGalaxies (BoRG) survey. BoRG has the largest area coverage to find luminous and\nrare z~8 sources that are among the first galaxies to have formed in the\nUniverse.", "category": "astro-ph_CO" }, { "text": "Episodic Star Formation Coupled to Reignition of Radio Activity in 3C\n 236: We present Hubble Space Telescope UV and optical imaging of the radio galaxy\n3C 236, whose relic 4 Mpc radio jet lobes and inner 2 kpc CSS radio source are\nevidence of multiple epochs of AGN activity. Our data confirm the presence of\nfour bright knots of FUV emission in an arc along the edge of the inner\ncircumnuclear dust disk in the galaxy's nucleus, as well as FUV emission\ncospatial with the nucleus itself. We interpret these to be sites of recent or\nongoing star formation. We present photometry of these knots, as well as an\nestimate for the internal extinction in the source using the Balmer decrement\nfrom SDSS spectroscopy. We estimate the ages of the knots by comparing our\nextinction-corrected photometry with stellar population synthesis models. We\nfind the four knots cospatial with the dusty disk to be young, of order 10^7 yr\nold. The FUV emission in the nucleus is likely due to an episode of star\nformation triggered ~10^9 yr ago. We argue that the young 10^7 yr old knots\nstem from an episode of star formation that was roughly coeval with the event\nresulting in reignition of radio activity, creating the CSS source. The 10^9 yr\nold stars in the nucleus may be associated with the previous epoch of activity\nthat generated the 4 Mpc relic source, before it was cut off by exhaustion or\ninterruption. The ages of the knots, considered in context with the disturbed\nmorphology of the nuclear dust and the double-double morphology of the \"old\"\nand \"young\" radio sources, present evidence for an episodic AGN/starburst\nconnection. We suggest that the AGN fuel supply was interrupted for ~10^7 yr\ndue to a minor merger event and has now been restored, and the resultant\nnon-steady flow of gas toward the nucleus is likely responsible for both the\nnew episode of infall-induced star formation and also the multiple epochs of\nradio activity.", "category": "astro-ph_CO" }, { "text": "Cosmological constraints from multiple tracers in spectroscopic surveys: We use the Fisher matrix formalism to study the expansion and growth history\nof the Universe using galaxy clustering with 2D angular cross-correlation\ntomography in spectroscopic or high resolution photometric redshift surveys.\nThe radial information is contained in the cross correlations between narrow\nredshift bins. We show how multiple tracers with redshift space distortions\ncancel sample variance and arbitrarily improve the constraints on the dark\nenergy equation of state $\\omega(z)$ and the growth parameter $\\gamma$ in the\nnoiseless limit. The improvement for multiple tracers quickly increases with\nthe bias difference between the tracers, up to a factor $\\sim4$ in\n$\\text{FoM}_{\\gamma\\omega}$. We model a magnitude limited survey with realistic\ndensity and bias using a conditional luminosity function, finding a factor\n1.3-9.0 improvement in $\\text{FoM}_{\\gamma\\omega}$ -- depending on global\ndensity -- with a split in a halo mass proxy. Partly overlapping redshift bins\nimprove the constraints in multiple tracer surveys a factor $\\sim1.3$ in\n$\\text{FoM}_{\\gamma\\omega}$. This findings also apply to photometric surveys,\nwhere the effect of using multiple tracers is magnified. We also show large\nimprovement on the FoM with increasing density, which could be used as a\ntrade-off to compensate some possible loss with radial resolution.", "category": "astro-ph_CO" }, { "text": "The early-type dwarf galaxy population of the Centaurus cluster: We present a photometric study of the early-type dwarf galaxy population of\nthe Centaurus cluster, aiming at investigating the galaxy luminosity function\n(LF) and galaxy scaling relations down to the regime of galaxies with M_V~-10\nmag. On deep VLT/FORS1 V- and I-band images of the central part of the cluster,\nwe identify cluster dwarf-galaxy candidates using both morphological and\nsurface brightness selection criteria. Photometric and structural parameters of\nthe candidates are derived from analysis of their surface brightness profiles.\nFundamental scaling relations, such as the colour-magnitude and the\nmagnitude-surface brightness relation, are used to distinguish the cluster from\nthe background. We find a flat LF with a slope of \\alpha = -1.14 \\pm 0.12 for\nM_V>-14 mag, when fitting a power law to the completeness-corrected galaxy\nnumber counts. When plotting the central surface brightness of a Sersic model\nvs. the galaxy magnitude, we find a continuous relation for magnitudes\n-20