Search

We characterize the conditional distributions of the HI gas-to-stellar mass ratio, $R_{HI}\equiv M_{HI}/M_{\ast}$, given the stellar mass, $M_{\ast}$, of local galaxies from $M_{\ast}\sim 10^7$ to $10^{12}$ $M_{\odot}$ separated into centrals and satellites as well as into late- and early-type galaxies (LTGs and ETGs, respectively). To do so, we use (1) the homogeneous "eXtended GALEX Arecibo SDSS Survey", xGASS (Catinella et al. 2018), by re-estimating their upper limits and taking into account them in our statistical analysis; and (2) the results from a large compilation of HI data reported in Calette et al. (2018). We use the $R_{HI}$ conditional distributions combined with the Galaxy Stellar Mass Function to infer the bivariate $M_{HI}$ and $M_{\ast}$ distribution of all galaxies as well of the late/early-type and central/satellite subsamples and their combinations. Satellites are on average less HI gas-rich than centrals at low and intermediate masses, with differences being larger for ETGs than LTGs; at $M_{\ast}>3-5\times 10^{10}$ $M_{\odot}$ the differences are negligible. The differences in the HI gas content are much larger between LTGs and ETGs than between centrals and satellites. Our empirical HI Mass Function is strongly dominated by central galaxies at all masses. The empirically constrained bivariate $M_{HI}$ and $M_{\ast}$ distributions presented here can be used to compare and constrain theoretical predictions as well as to generate galaxy mock catalogues., In press, 21 pages, 15 figures. Minor corrections in text, results unchanged. Supplementary material available at ancillary files

The mean size ( effective radius $R_e$) of Massive Galaxies (MGs, $M_{\rm star}>10^{11.2}M_\odot$) is observed to increase steadily with cosmic time. It is still unclear whether this trend originates from the size growth of individual galaxies (via, e.g., mergers and/or AGN feedback) or from the inclusion of larger galaxies entering the selection at later epochs (progenitor bias). We here build a data-driven, flexible theoretical framework to probe the structural evolution of MGs. We assign galaxies to dark matter haloes via stellar mass-halo mass (SMHM) relations with varying high-mass slopes and scatters $\sigma_{\rm SMHM}$ in stellar mass at fixed halo mass, and assign sizes to galaxies using an empirically-motivated, constant and linear relationship between $R_e$ and the host dark matter halo radius $R_h$. We find that: 1) the fast mean size growth of MGs is well reproduced independently of the shape of the input SMHM relation; 2) the numbers of compact MGs grow steadily until $z\gtrsim2$ and fall off at lower redshifts, suggesting a lesser role of progenitor bias at later epochs; 3) a time-independent scatter $\sigma_{\rm SMHM}$ is consistent with a scenario in which compact starforming MGs transition into quiescent MGs in a few $10^8$yr with a negligible structural evolution during the compact phase, while a scatter increasing at high redshift implies significant size growth during the starforming phase. A robust measurement of the size function of MGs at high redshift can set strong constraints on the scatter of the SMHM relation and, by extension, on models of galaxy evolution., Comment: Accepted for publication in MNRAS. Comments still welcome

We extend the local stellar galaxy-(sub)halo connection to the atomic hydrogen (HI) component by seeding semi-empirically galaxies into a large N-body dark matter (DM) simulation. The main input to construct the mock galaxy catalogue are: our constrained stellar mass-to-(sub)halo circular velocity ($M_{\ast}$-$V_{\rm DM}$) relation, assuming a scatter independent of any galaxy property, and the empirical $M_{\rm HI}$ conditional probability distributions given $M_{\ast}$ for central and satellite galaxies. We find that the $\langle\log M_{\rm HI}\rangle-\log M_{\rm DM}$ relation is not a monotonic increasing function. It increases with mass up to $M_{\rm DM}\sim 10^{12}$ $M_{\odot}$, attaining a maximum of $\langle\log(M_{\rm HI}/M_{\odot})\rangle \sim 9.2$, and at higher (sub)halo masses, $\langle\log(M_{\rm HI})\rangle$ decreases slightly with $M_{\rm DM}$. The scatter around it is also large and mass dependent. The bivariate $M_{\rm HI}$ and $M_{\rm DM}$ distribution is broad and bimodal, specially at $M_{\rm DM}\gtrsim 10^{12}$ $M_\odot$, which is inherited from the input $M_{\rm HI}$ conditional distributions. We also report the total (central+satellites) HI gas mass within halos, $\langle M^{\rm tot}_{\rm HI}(M_{\rm DM})\rangle$, as a function of $M_{\rm DM}$. The mean $M^{\rm tot}_{\rm HI}-M_{\rm DM}$ relation is an increasing monotonic function. The galaxy spatial clustering increases weakly as the $M_{\rm HI}$ threshold increases. Our HI mock galaxies cluster more in comparison to the blind HI ALFALFA (Arecibo Fast Legacy ALFA) survey but we show that it is mainly due to the selection effects. We discuss the implications of our results in the light of predictions from semi-analytical models and hydrodynamics simulations of galaxy evolution., Comment: In press, 20 pages, 19 figures. Some corrections in text, references added. Results unchanged

Cold Dark Matter with cosmological constant (ΛCDM) cosmological models with early dark energy (EDE) have been proposed to resolve tensions between the Hubble constant H 0=100, h km -1pc-1 measured locally, giving h ≈ 0.73, and H0 deduced from Planck cosmic microwave background (CMB) and other early-Universe measurements plus ΛCDM, giving h ≈ 0.67. EDE models do this by adding a scalar field that temporarily adds dark energy equal to about 10 per cent of the cosmological energy density at the end of the radiation-dominated era at redshift z ∼3500. Here, we compare linear and non-linear predictions of a Planck-normalized ΛCDM model including EDE giving h = 0.728 with those of standard Planck-normalized ΛCDM with h = 0.678. We find that non-linear evolution reduces the differences between power spectra of fluctuations at low redshifts. As a result, at z = 0 the halo mass functions on galactic scales are nearly the same, with differences only 1-2 per cent. However, the differences dramatically increase at high redshifts. The EDE model predicts 50 per cent more massive clusters at z = 1 and twice more galaxy-mass haloes at z = 4. Even greater increases in abundances of galaxy-mass haloes at higher redshifts may make it easier to reionize the universe with EDE. Predicted galaxy abundances and clustering will soon be tested by the James Webb Space Telescope (JWST) observations. Positions of baryonic acoustic oscillations (BAOs) and correlation functions differ by about 2 per cent between the models-an effect that is not washed out by non-linearities. Both standard ΛCDM and the EDE model studied here agree well with presently available acoustic-scale observations, but the Dark Energy Spectroscopic Instrument and Euclid measurements will provide stringent new tests. © 2021 The Author(s)., AK and FP thank the support of the Spanish Ministry of Science funding grant PGC2018-101931-B-I00. This work used the skun6@IAA facility managed by the Instituto de Astrofísica de Andalucía (CSIC). The equipment was funded by the Spanish Ministry of Science EU-FEDER infrastructure grantEQC2018-004366-P. MK acknowledges the support of NSF Grant No. 1519353, NASA NNX17AK38G, and the Simons Foundation. TLS acknowledges support from NASA (through grant 80NSSC18K0728) and the Research Corporation. We thank Alexie Leauthaud and Johannes Lange for a helpful discussion about weak lensing results., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

We report the bivariate $\rm HI$ - and $\rm H_{2}$ -stellar mass distributions of local galaxies in addition of an inventory of galaxy mass functions, MFs, for $\rm HI$ , $\rm H_{2}$ , cold gas, and baryonic mass, separately into early- and late-type galaxies. The MFs are determined using the $\rm HI$ and $\rm H_{2}$ conditional distributions and the galaxy stellar mass function (GSMF). For the conditional distributions we use the results from the compilation presented in Calette et al. [(2018) RMxAA, 54, 443.]. For determining the GSMF from $M_{*}\sim3\times10^{7}$ to $3\times10^{12}\ \text{M}_{\odot}$ , we combine two spectroscopic samples from the Sloan Digital Sky Survey at the redshift range $0.0033 . We find that the low-mass end slope of the GSMF, after correcting from surface brightness incompleteness, is $\alpha\approx-1.4$ , consistent with previous determinations. The obtained $\rm HI\,$ MFs agree with radio blind surveys. Similarly, the $\rm H_{2}\,$ MFs are consistent with CO follow-up optically-selected samples. We estimate the impact of systematics due to mass-to-light ratios and find that our MFs are robust against systematic errors. We deconvolve our MFs from random errors to obtain the intrinsic MFs. Using the MFs, we calculate cosmic density parameters of all the baryonic components. Baryons locked inside galaxies represent 5.4% of the universal baryon content, while $\sim\! 96\%$ of the $\rm HI$ and $\rm H_{2}$ mass inside galaxies reside in late-type morphologies. Our results imply cosmic depletion times of $\rm H_{2}$ and total neutral H in late-type galaxies of $\sim\!1.3$ and 7.2 Gyr, respectively, which shows that late type galaxies are on average inefficient in converting $\rm H_{2}$ into stars and in transforming $\rm HI$ gas into $\rm H_{2}$ . Our results provide a fully self-consistent empirical description of galaxy demographics in terms of the bivariate gas–stellar mass distribution and their projections, the MFs. This description is ideal to compare and/or to constrain galaxy formation models.

This paper is one in a series that explores the importance of radius as a second parameter in galaxy evolution. The topic investigated here is the relationship between star formation rate (SFR) and galaxy radius (R-e) for main-sequence star-forming galaxies. The key observational result is that, over a wide range of stellar mass and redshift in both CANDELS and SDSS, there is little correlation between SFR and R-e at fixed stellar mass. The Kennicutt-Schmidt law, or any similar density-related star formation law, then implies that smaller galaxies must have lower gas fractions than larger galaxies (at fixed M-*), and this is supported by observations of gas in local star-forming galaxies. We investigate the implications by adopting the equilibrium "bathtub" model: the ISM gas mass is assumed to be constant over time, and the net SFR is the difference between the accretion rate of gas onto the galaxy from the halo and the outflow rate due to winds. To match the observed null correlation between SFR and radius, the bathtub model requires that smaller galaxies at fixed mass have weaker galactic winds. Our hypothesis is that galaxies are a two-parameter family whose properties are set mainly by halo mass and concentration. These determine the radius and gas accretion rate, which in turn predict how wind strength needs to vary with R-e to keep the SFR constant.

An analytical approach is proposed to study the evolution of the star-forming galaxy (SFG) main sequence (MS) and the fraction of dust-obscured SF up to $z\sim4$. Far-ultraviolet (FUV) and infrared (IR) star formation rates, SFRs, are described as conditional probability functions of $M_{\ast}$. We convolve them with the galaxy stellar mass function (GSMF) of SFGs to derive the FUV and IR LFs. The 2 SF modes formalism is used to describe starburst galaxies. By fitting observed FUV and IR LFs, the parametrization of SFR$_{\rm FUV}-M_{\ast}$ and SFR$_{\rm IR}-M_{\ast}$ are constrained. Our derived SFR$_{\rm FUV+IR}-M_{\ast}$ reproduces the evolution of the MS as compared to other observational inferences. At any redshift, we find that the sSFR$_{\rm FUV+IR}-M_{\ast}$ relation for MS SFGs approaches to a power law at the high-mass end. At lower masses, it bends and eventually the slope sign changes from negative to positive at very low masses. At $z\sim0$, this change of sign is at $M_{\ast}\sim5\times10^{8}{\rm M}_{\odot}$ close to dust-obscured SF regime, $M_{\ast}\sim6\times10^{8}{\rm M}_{\odot}$. The slope sign change is related to the knee of the FUV LF. Our derived dust-obscured fractions agree with previous determinations at $0\leq z\leq2.5$. Dust-obscured fractions depend strongly on mass with almost no dependence with redshift at $z\gtrsim1.2$. At $z\lesssim0.75$ high-mass galaxies become more "transparent" compared to their high redshift counterparts. On the opposite, low- and intermediate-mass galaxies have become more obscured by dust. The joint evolution of the GSMF and the FUV and IR LFs is a promising approach to study mass growth and dust formation/destruction mechanisms., Comment: Submitted to ApJ, 20 pages, 12 figures. Comments are welcome. This is an improved version after the first Referee report. Results remained unchanged

By means of post-processed cosmological Hydrodynamics simulations we explore the ability of the fossil record method to recover the stellar mass, age gradients, and global/radial star formation and mass growth histories of galaxies observed with an optical Integral Field Unity. We use two simulations of representative Milky Way-sized galaxies, one disk dominated and another bulge-dominated. We generate data cubes emulating MaNGA/SDSS-IV instrumental and observational conditions, and analyze them using the Pipe3D pipeline. For optimal MaNGA instrumental/observational setups, the global masses, ages, and dust extinctions of both galaxies are well recovered within the uncertainties, while for the radial distributions, the trend is to get slightly flatter age gradients and weaker inside-out growth modes than the true ones. The main bias is in recovering younger stellar populations in the inner, older regions, and slightly older stellar populations in the outer, younger regions, as well as lower global stellar masses. These trends are enhanced as lower is the spatial sampling/resolution (less number of fibers), more inclined and dust-attenuated is the observed galaxy, lower is the signal-to-noise ratio, and worse is the seeing. The recovered properties and histories are more affected for the disk-dominated galaxy with a prominent inside-out growth mode than for the bulge-dominated galaxy assembled earlier and more coherently. We make publicly available the code and the mock IFU datacubes used in this paper., Comment: Accepted for publication to MNRAS

We study the properties of distinct dark matter halos (i.e., those that are not subhalos) that have a final virial mass $M_{\mathrm{vir}}$ at $z = 0$ less than their peak mass ($M_{\mathrm{peak}}$) in the Bolshoi-Planck cosmological simulation. We identify two primary causes of halo mass loss: relaxation after a major merger and tidal stripping by a massive neighbouring halo. Major mergers initially boost $M_{\mathrm{vir}}$ and typically cause the final halo to become more prolate and less relaxed and to have higher spin and lower NFW concentration. As the halo relaxes, high energy material from the recent merger gradually escapes beyond the virial radius, temporarily resulting in a net negative accretion rate that reduces the halo mass by $5-15\%$ on average. Halos that experience a major merger around $z = 0.4$ typically reach a minimum mass near $z = 0$. Tidal stripping mainly occurs in dense regions, and it causes halos to become less prolate and have lower spins and higher NFW concentrations. Tidally stripped halos often lose a large fraction of their peak mass ($> 20\%$) and most never recover (or even reattain a positive accretion rate). Low mass halos can be strongly affected by both post-merger mass loss and tidal stripping, while high mass halos are predominantly influenced by post-merger mass loss and show few signs of significant tidal stripping.

We present new determinations of the stellar-to-halo mass relation (SHMR) at $z=0-10$ that match the evolution of the galaxy stellar mass function, the SFR$-M_*$ relation,and the cosmic star formation rate. We utilize a compilation of 40 observational studies from the literature and correct them for potential biases. Using our robust determinations of halo mass assembly and the SHMR, we infer star formation histories, merger rates, and structural properties for average galaxies, combining star-forming and quenched galaxies. Our main findings: (1) The halo mass $M_{50}$ above which 50\% of galaxies are quenched coincides with sSFR/sMAR$\sim1$, where sMAR is the specific halo mass accretion rate. (2) $M_{50}$ increases with redshift, presumably due to cold streams being more efficient at high redshift while virial shocks and AGN feedback become more relevant at lower redshifts. (3) The ratio sSFR/sMAR has a peak value, which occurs around $M_{\rm vir}\sim2\times10^{11}M_{\odot}$. (4) The stellar mass density within 1 kpc, $\Sigma_1$, is a good indicator of the galactic global sSFR. (5) Galaxies are statistically quenched after they reach a maximum in $\Sigma_1$, consistent with theoretical expectations of the gas compaction model; this maximum depends on redshift. (6) In-situ star formation is responsible for most galactic stellar mass growth, especially for lower-mass galaxies. (7) Galaxies grow inside out. The marked change in the slope of the size--mass relation when galaxies became quenched, from $d\log R_{\rm eff}/d\log M_*\sim0.35$ to $\sim2.5$, could be the result of dry minor mergers.

We investigate the dependence of the galaxy-halo connection and galaxy density field in modified gravity models using the $N-$body simulations for $f(R)$ and nDGP models at $z=0$. Because of the screening mechanisms employed by these models, chameleon and Vainshtein, halos are clustered differently in the non-linear regime of structure formation. We quantify their deviations in the galaxy density field from the standard $\Lambda$CDM model under different environments. We populate galaxies in halos via the (Sub)Halo Abundance Matching. Our main results are: 1) The galaxy-halo connection {\it strongly} depends on the gravity model; a maximum variation of $\sim40\%$ is observed between Halo Occupational Distribution (HOD) parameters; 2) $f(R)$ gravity models predict an excess of galaxies in low density environments of $\sim10\%$ but predict a deficit of $\sim10\%$ at high density environments for $|f_{R0}| = 10^{-4}$ and $10^{-6}$ while $|f_{R0}| = 10^{-5}$ predicts more high density structures; nDGP models are consistent with $\Lambda$CDM; 3) Different gravity models predict different dependences of the galaxy luminosity function (GLF) with the environment, especially in void-like regions we find differences around $\sim10\%$ for the $f(R)$ models while nDPG models remain closer to $\Lambda$CDM for low-luminosity galaxies but there is a deficit of $\sim11\%$ for high-luminosity galaxies in all environments. We conclude that the dependence of the GLF with environment might provide a test to distinguish between gravity models and their screening mechanisms from the $\Lambda$CDM. We provide HOD parameters for the gravity models analyzed in this paper., Comment: 22 pages, 14 figures, 4 tables

Existing models of galaxy formation have not yet explained striking correlations between structure and star-formation activity in galaxies, notably the sloped and moving boundaries that divide star-forming from quenched galaxies in key structural diagrams. This paper uses these and other relations to ``reverse-engineer'' the quenching process for central galaxies. The basic idea is that star-forming galaxies with larger radii (at a given stellar mass) have lower black-hole masses due to lower central densities. Galaxies cross into the green valley when the cumulative effective energy radiated by their black hole equals $\sim4\times$ their halo-gas binding energy. Since larger-radii galaxies have smaller black holes, one finds they must evolve to higher stellar masses in order to meet this halo-energy criterion, which explains the sloping boundaries. A possible cause of radii differences among star-forming galaxies is halo concentration. The evolutionary tracks of star-forming galaxies are nearly parallel to the green-valley boundaries, and it is mainly the sideways motions of these boundaries with cosmic time that cause galaxies to quench. BH-scaling laws for star-forming, quenched, and green-valley galaxies are different, and most BH mass growth takes place in the green valley. Implications include: the radii of star-forming galaxies are an important second parameter in shaping their black holes; black holes are connected to their halos but in different ways for star-forming, quenched, and green-valley galaxies; and the same BH-halo quenching mechanism has been in place since $z \sim 3$. We conclude with a discussion of black hole-galaxy co-evolution, the origin and interpretation of BH scaling laws., 45 pages, 20 figures, 2 tables, accepted for publication in ApJ

We study the global star-formation rate (SFR) vs. stellar mass (M$_*$) correlation, and the spatially-resolved SFR surface density ($\Sigma_{SFR}$) vs. stellar mass surface density (\Sm) correlation, in a sample of $\sim2,000$ galaxies from the MaNGA MPL-5 survey. We classify galaxies and spatially-resolved areas into star-forming and retired according to their ionization processes. We confirm the existence of a Star-Forming Main Sequence (SFMS) for galaxies and spatially-resolved areas, and show that they have the same nature, with the global as a consequence of the local one. The latter presents a bend below a limit \Sm value, $\approx 3\times 10^7$ M$_\odot$kpc$^{-2}$, which is not physical. Using only star-forming areas (SFAs) above this limit, a slope and a scatter of $\approx1$ and $\approx0.27$ dex are determined. The retired galaxies/areas strongly segregate from their respective SFMS's, by $\sim -1.5$ dex on average. We explore how the global/local SFMS's depend on galaxy morphology, finding that for star-forming galaxies and SFAs, there is a trend to lower values of star-formation activity with earlier morphological types, which is more pronounced for the local SFMS. The morphology not only affects the global SFR due to the diminish of SFAs with earlier types, but also affects the local SF process. Our results suggest that the local SF at all radii is established by some universal mechanism partially modulated by morphology. Morphology seems to be connected to the slow aging and sharp decline of the SF process, and on its own it may depend on other properties as the environment., Comment: 24 pages, 16 figues. Accepted to appear in MNRAS

This paper studies pseudo-bulges (P-bulges) and classical bulges (C-bulges) in Sloan Digital Sky Survey central galaxies using the new bulge indicator $\Delta\Sigma_1$, which measures relative central stellar-mass surface density within 1 kpc. We compare $\Delta\Sigma_1$ to the established bulge-type indicator $\Delta\langle\mu_e\rangle$ from Gadotti (2009) and show that classifying by $\Delta\Sigma_1$ agrees well with $\Delta\langle\mu_e\rangle$. $\Delta\Sigma_1$ requires no bulge-disk decomposition and can be measured on SDSS images out to $z = 0.07$. Bulge types using it are mapped onto twenty different structural and stellar-population properties for 12,000 SDSS central galaxies with masses 10.0 < log $M_*$/$M_{\odot}$ < 10.4. New trends emerge from this large sample. Structural parameters show fairly linear log-log relations vs. $\Delta\Sigma_1$ and $\Delta\langle\mu_e\rangle$ with only moderate scatter, while stellar-population parameters show a highly non-linear "elbow" in which specific star-formation rate remains roughly flat with increasing central density and then falls rapidly at the elbow, where galaxies begin to quench. P-bulges occupy the low-density end of the horizontal arm of the elbow and are universally star-forming, while C-bulges occupy the elbow and the vertical branch and exhibit a wide range of star-formation rates at fixed density. The non-linear relation between central density and star-formation rate has been seen before, but this mapping onto bulge class is new. The wide range of star-formation rates in C-bulges helps to explain why bulge classifications using different parameters have sometimes disagreed in the past. The elbow-shaped relation between density and stellar indices suggests that central structure and stellar-populations evolve at different rates as galaxies begin to quench., Comment: 23 pages, 17 figures, published in MNRAS

We study the rest-frame optical mass–size relation of bulges and discs from z ∼ 2 to z ∼ 0 for a complete sample of massive galaxies in the CANDELS fields using two-component Sérsic models. Discs and star-forming galaxies follow similar mass–size relations. The mass–size relation of bulges is less steep than the one of quiescent galaxies (best-fitting slope of 0.7 for quiescent galaxies against 0.4 for bulges). We find little dependence of the structural properties of massive bulges and discs with the global morphology of galaxies (disc versus bulge dominated) and the star formation activity (star-forming versus quiescent). This result suggests similar bulge formation mechanisms for most massive galaxies and also that the formation of the bulge component does not significantly affect the disc structure. Our results pose a challenge to current cosmological models that predict distinct structural properties for stellar bulges arising from mergers and disc instabilities., This work has been essentially funded by to a French national PhD scholarship. MHC is also thankful to Google for their unrestricted gift to explore deep-learning techniques for galaxy evolution. PGP-G acknowledges support from the Spanish Government grant AYA2015-63650-P. FS acknowledges partial support from a Leverhulme Trust Research Fellowship.

We study how properties of discrete dark matter halos depend on halo environment, characterized by the mass density around the halos on scales from 0.5 to 16 $h^{-1}{\rm Mpc}$. We find that low mass halos (those less massive than the characteristic mass $M_{\rm C}$ of halos collapsing at a given epoch) in high-density environments have lower accretion rates, lower spins, higher concentrations, and rounder shapes than halos in median density environments. Halos in median and low-density environments have similar accretion rates and concentrations, but halos in low density environments have lower spins and are more elongated. Halos of a given mass in high-density regions accrete material earlier than halos of the same mass in lower-density regions. All but the most massive halos in high-density regions are losing mass (i.e., being stripped) at low redshifts, which causes artificially lowered NFW scale radii and increased concentrations. Tidal effects are also responsible for the decreasing spins of low mass halos in high density regions at low redshifts $z < 1$, by preferentially removing higher angular momentum material from halos. Halos in low-density regions have lower than average spins because they lack nearby halos whose tidal fields can spin them up. We also show that the simulation density distribution is well fit by an Extreme Value Distribution, and that the density distribution becomes broader with cosmic time., 27 pages, 20 figures

We report and provide fitting functions for the abundance of dark matter halos and subhalos as a function of mass, circular velocity, and redshift from the new Bolshoi-Planck and MultiDark-Planck $\Lambda$CDM cosmological simulations, based on the Planck cosmological parameters. We also report the halo mass accretion rates, which may be connected with galaxy star formation rates. We show that the higher cosmological matter density of the Planck parameters compared with the WMAP parameters leads to higher abundance of massive halos at high redshifts. We find that the median halo spin parameter $\lambda_{\rm B} = J(2M_{\rm vir}R_{\rm vir}V_{\rm vir})^{-1}$ is nearly independent of redshift, leading to predicted evolution of galaxy sizes that is consistent with observations, while the significant decrease with redshift in median $\lambda_{\rm P} = J|E|^{-1/2}G^{-1}M^{-5/2}$ predicts more decrease in galaxy sizes than is observed. Using the Tully-Fisher and Faber-Jackson relations between galaxy velocity and mass, we show that a simple model of how galaxy velocity is related to halo maximum circular velocity leads to increasing overprediction of cosmic stellar mass density as redshift increases beyond redshifts $z\sim1$, implying that such velocity-mass relations must change at redshifts $z>1$. By making a realistic model of how observed galaxy velocities are related to halo circular velocity, we show that recent optical and radio observations of the abundance of galaxies are in good agreement with our $\Lambda$CDM simulations. Our halo demographics are based on updated versions of the \rockstar\ and \ctrees\ codes, and this paper includes appendices explaining all of their outputs. This paper is an introduction to a series of related papers presenting other analyses of the Bolshoi-Planck and MultiDark-Planck simulations., Comment: 27 pages, 26 figures. To match the published version at MNRAS. Rockstar and Consistent Trees outputs are available at http://hipacc.ucsc.edu/Bolshoi/MergerTrees.html

Understanding how bulges grow in galaxies is critical step towards unveiling the link between galaxy morphology and star-formation. To do so, it is necessary to decompose large sample of galaxies at different epochs into their main components (bulges and disks). This is particularly challenging, especially at high redshifts, where galaxies are poorly resolved. This work presents a catalog of bulge-disk decompositions of the surface brightness profiles of ~17.600 H-band selected galaxies in the CANDELS fields (F160W, Comment: 18 pages, 18 figures, 3 table, submitted to MNRAS after the first referee's report

We study the effects of the local environmental density and the cosmic web environment (filaments, walls, and voids) on key properties of dark matter halos using the Bolshoi-Planck LCDM cosmological simulation. The z = 0 simulation is analysed into filaments, walls, and voids using the SpineWeb method and also the VIDE package of tools, both of which use the watershed transform. The key halo properties that we study are the specific mass accretion rate, spin parameter, concentration, prolateness, scale factor of the last major merger, and scale factor when the halo had half of its z = 0 mass. For all these properties, we find that there is no discernible difference between the halo properties in filaments, walls, or voids when compared at the same environmental density. As a result, we conclude that environmental density is the core attribute that affects these properties. This conclusion is in line with recent findings that properties of galaxies in redshift surveys are independent of their cosmic web environment at the same environmental density at z ~ 0. We also find that the local web environment of the Milky Way and the Andromeda galaxies near the centre of a cosmic wall does not appear to have any effect on the properties of these galaxies' dark matter halos except for their orientation, although we find that it is rather rare to have such massive halos near the centre of a relatively small cosmic wall., Comment: 23 pages

We study the global and radial stellar mass assembly of eight zoomed-in MW-sized galaxies produced in Hydrodynamics cosmological simulations. The disk-dominated galaxies (4) show a fast initial stellar mass growth in the innermost parts, driven mostly by in-situ SF, but since $z\sim2-1$ the SF enters in a long-term quenching phase. The outer regions follow this trend but more gentle as more external they are. As the result, the radial stellar mass growth is highly inside-out due to both the inside-out structural growth and inside-out SF quenching. The half-mass radius evolves fast; for instance, $R_{0.5}$($z=1$)$, 23 pages, 15 figures. Accepted for publication in ApJ. Minor corrections and more references added. The discussion was extended in section 6.1

SubHalo Abundance Matching (SHAM) assumes that one (sub)halo property, such as mass Mvir or peak circular velocity Vpeak, determines properties of the galaxy hosted in each (sub)halo such as its luminosity or stellar mass. This assumption implies that the dependence of Galaxy Luminosity Functions (GLFs) and the Galaxy Stellar Mass Function (GSMF) on environmental density is determined by the corresponding halo density dependence. In this paper, we test this by determining from an SDSS sample the observed dependence with environmental density of the ugriz GLFs and GSMF for all galaxies, and for central and satellite galaxies separately. We then show that the SHAM predictions are in remarkable agreement with these observations, even when the galaxy population is divided between central and satellite galaxies. However, we show that SHAM fails to reproduce the correct dependence between environmental density and g-r color for all galaxies and central galaxies, although it better reproduces the color dependence on environmental density of satellite galaxies., 21 pages, 11 figures. Accepted for publication in MNRAS

We investigate the environmental quenching of galaxies, especially those with stellar masses (M*)$10^{10.5} M_\odot$) within a redshift range. At a given redshift and M*, the environmental quenching effect is considered to be observed if the $d_{proj}$ distribution of QGs ($d_{proj}^Q$) is significantly skewed toward lower values than that of star-forming galaxies ($d_{proj}^{SF}$). For galaxies with $10^{8} M_\odot < M* < 10^{10} M_\odot$, such a difference between $d_{proj}^Q$ and $d_{proj}^{SF}$ is detected up to $z\sim1$. Also, about 10\% of the quenched galaxies in our sample are located between two and four virial radii ($R_{Vir}$) of the massive halos. The median projected distance from low-mass QGs to their massive neighbors, $d_{proj}^Q / R_{Vir}$, decreases with satellite M* at $M* \lesssim 10^{9.5} M_\odot$, but increases with satellite M* at $M* \gtrsim 10^{9.5} M_\odot$. This trend suggests a smooth, if any, transition of the quenching timescale around $M* \sim 10^{9.5} M_\odot$ at $0.5, 8 pages, 5 figures. ApJL accepted. Typos corrected

We present a simple, efficient and robust approach to improve cosmological redshift measurements. The method is based on the presence of a reference sample for which a precise redshift number distribution (dN/dz) can be obtained for different pencil-beam-like sub-volumes within the original survey. For each sub-volume we then impose: (i) that the redshift number distribution of the uncertain redshift measurements matches the reference dN/dz corrected by their selection functions; and (ii) the rank order in redshift of the original ensemble of uncertain measurements is preserved. The latter step is motivated by the fact that random variables drawn from Gaussian probability density functions (PDFs) of different means and arbitrarily large standard deviations satisfy stochastic ordering. We then repeat this simple algorithm for multiple arbitrary pencil-beam-like overlapping sub-volumes; in this manner, each uncertain measurement has multiple (non-independent) "recovered" redshifts which can be used to estimate a new redshift PDF. We refer to this method as the Stochastic Order Redshift Technique (SORT). We have used a state-of-the-art N-body simulation to test the performance of SORT under simple assumptions and found that it can improve the quality of cosmological redshifts in an efficient and robust manner. Particularly, SORT redshifts are able to recover the distinctive features of the 'cosmic web' and can provide unbiased measurement of the two-point correlation function on scales > 4 Mpc/h. Given its simplicity, we envision that a method like SORT can be incorporated into more sophisticated algorithms aimed to exploit the full potential of large extragalactic photometric surveys., MNRAS accepted; 15 pages, 9 figures

The galaxy stellar-to-halo mass relation (SHMR) is nearly time-independent for $z < 4$. We therefore construct a time-independent SHMR model for central galaxies, wherein the in-situ star formation rate (SFR) is determined by the halo mass accretion rate (MAR), which we call Stellar-Halo Accretion Rate Coevolution (SHARC). We show that the $\sim0.3$ dex dispersion of the halo MAR matches the observed dispersion of the SFR on the star-formation main sequence (MS). In the context of "bathtub"-type models of galaxy formation, SHARC leads to mass-dependent constraints on the relation between SFR and MAR. Despite its simplicity and the simplified treatment of mass growth from mergers, the SHARC model is likely to be a good approximation for central galaxies with $M_*=10^9- 10^{10.5}M_\odot$ that are on the MS, representing most of the star formation in the Universe. SHARC predictions agree with observed SFRs for galaxies on the MS at low redshifts, agree fairly well at $z\sim4$, but exceed observations at $z>4$. Assuming that the interstellar gas mass is constant for each galaxy (the "equilibrium condition" in bathtub models), the SHARC model allows calculation of net mass loading factors for inflowing and outflowing gas. With assumptions about preventive feedback based on simulations, SHARC allows calculation of galaxy metallicity evolution. If galaxy SFRs indeed track halo MARs, especially at low redshifts, that may help explain the success of models linking galaxy properties to halos (including age-matching) and the similarities between two-halo galaxy conformity and halo mass accretion conformity., Accepted for publication in MNRAS. No substantial changes. Abstract slightly modified in order to match the MNRAS Abstract length limit of 250 words. 18 pages, 12 figures

We perform an exhaustive comparison among central galaxies from SDSS catalogs in different local environments at 0.01, 17 pages, 11 figures after last Referee's report. Accepted for publication in ApJ

We present high-resolution N-body/hydrodynamics simulations of dwarf galaxies formed in isolated CDM halos with the same virial mass, Mv~2.5x10^10 Msun at z=0, in order to (1) study the mass assembly histories (MAHs) of the halo, stars, and gas components, and (2) explore the effects of the halo MAHs on the stellar/baryonic assembly of the simulated dwarfs and on their z~0 properties. Overall, the simulated dwarfs are roughly consistent with observations. Our main results are: a) The stellar-to-halo mass ratio is ~0.01 and remains roughly constant since z~1 (the stellar MAHs follow closely the halo MAHs), with a smaller value at higher z's for those halos that assemble their mass later. b) The evolution of the galaxy gas fraction, fg, is episodic and higher, most of the time, than the stellar fraction. When fg decreases (increases), the gas fraction in the halo typically increases (decreases), showing that the SN driven outflows play an important role in regulating the gas fractions -and hence the SFR- of the dwarfs. However, in most cases, an important fraction of the gas escapes the virial radius, Rv; at z=4 the total baryon fraction inside Rv is 1.5-2 times smaller than the universal one, while at z=0 is 2-6 times smaller, with the earlier assembled halos ejecting more gas. c) The SF histories are episodic with changes in the SFRs of factors 2-10 on average. d) Although the dwarfs formed in late assembled halos show more extended SF histories, their z~0 SFRs are still below the ones measured for local isolated dwarfs. e) The effects of baryons on Mv are such that at almost any time Mv is 10-20% smaller than the corresponding Mv obtained in pure N-body simulations. Our results suggest that rather than increasing the strength of the SN-driven outflows, processes that reduce the SF efficiency even more will help to solve the potential issues faced by the CDM-based simulations of dwarfs., 14 pages, 12 figures. ApJ, published. Minor changes after final Referee's report

Several occupational distributions for satellite galaxies more massive than ms~4E7 Msun around MW-sized hosts are presented and used to predict their internal dynamics. For this, a galaxy group mock catalog is constructed on the basis of (sub)halo-to-stellar mass relations constrained with the observed Galaxy Stellar Mass Function decomposed into centrals and satellites, and the 2-point correlation functions. For the MW-sized hosts we find that: 6.6% have 2 satellites in the SMC-LMC mass range; their probabilities to have 1, 2 or 3 satellites equal or larger than the LMC, the SMC or Sgr, respectively, are 0. 26, 0. 14, and 0. 14; those hosts with 3 satellites >= Sgr (as the MW) are among the most common cases, though the most and 2nd most massive satellites in these systems are SMALLER than the LMC and SMC by 0.7 and 0.8 dex, respectively. The cumulative satellite mass function is quite broad, the particular configuration of the MW being of low frequency but NOT an outlier (it is within the upper 1sig yet). For the MW satellite configuration, we constrain the halo mass to be Mh>1.4E12 Msun (1sig level). We find that the abundance of massive subhalos should agree with the abundance of massive satellites in all MW-sized hosts (there is not a massive satellite missing problem for LCDM). However, the vmax of the subhalos of satellites with ms, 10 pages, 6 figures. Accepted for publication in ApJ. arXiv abstract improved

We infer the local stellar-to-halo/subhalo mass relations (MRs) for central and satellite galaxies separately. We constraint this relations by using several combinations of observational data, consisting of the total galaxy stellar mass function, its decomposition into centrals and satellites, and the projected two-point correlation functions measured in different stellar mass bins. The differences among the resulting MRs are within the model-fit uncertainties (which are very small, smaller than the intrinsic scatter between galaxy and halo mass), no matter what combination of data are used. We also constrain the values of the intrinsic scatter around the central-halo (CH) and satellite-subhalo (SS) MRs assuming them to be constant: sigma_c= 0.168+-0.051 dex and sigma_s = 0.172+-0.057 dex, respectively. The CH and SS MRs are actually different, in particular when we take the subhalo mass at the present-day epoch instead of at their accretion time. We calculate several population statistics. We find that the central galaxy is not on average within the mass distribution of the most-massive satellite, even for cluster-sized halos, i.e., centrals are not a mere realization of the high-end of the satellite mass function; however for > 3x10^13 msun halos, ~15% of centrals could be. We also find that the probabilities of MW-sized halos of having N Magellanic-Clouds (MCs)-sized satellites agree well with observational measures; for a halo mass of 2x10^12 msun, the probability to have 2 MCs is 5.4%, but if we exclude those systems with satellites larger than the MCs, then the probability decreases to, 18 pages, 7 figures. Accepted for publication in ApJ. Some references were added

We extend the abundance matching technique (AMT) to infer the satellite-subhalo and central-halo mass relations (MRs) of galaxies, as well as the corresponding satellite conditional mass functions (CMFs). We use the observed galaxy stellar mass function (GSMF) decomposed into centrals and satellites and the LCDM halo/subhalo mass functions as inputs. We explore the effects of defining the subhalo mass at the time of accretion (m_acc) vs. at the time of observation (m_obs). We test the standard assumption that centrals and satellites follow the same MRs, showing that this assumption leads to predictions in disagreement with observations, specially for m_obs. Instead, when the satellite-subhalo MRs are constrained following our AMT, they are always different from the central-halo MR: the smaller the stellar mass (Ms), the less massive is the subhalo of satellites as compared to the halo of centrals of the same Ms. On average, for Ms, 13, pages, 4 figures. Accepted for publication in ApJ. Minor changes to previous version

The observations show that less massive the galaxies are, the higher on average is their specific star formation rate (SSFR = SFR/Ms, Ms is the stellar mass). Such a trend, called the 'SSFR downsizing' (SSFR-DS) phenomenon, is seen for local and high-z (back to z~1-2) galaxy samples. We use observational data related only to disc galaxies and explore the average SSFR change with z for different masses. For Ms in the range ~10^9.5-10^10.5 Msun, the SSFR increases with (1+z) to a power that barely depends on Ms, and at all z's smaller galaxies have ever higher SSFRs. The latter strongly disagree with the LCDM hierarchical mass accretion rates. By means of self-consistent models of disc galaxy evolution inside growing LCDM halos, the effects that disc feedback-driven outflows and gas re-accretion have on the galaxy SSFR histories are explored. The parameters of the outflow and re-accretion schemes are tuned to reproduce the z~0 Mh-Ms relation inferred from observations. In the case of outflows only, the SSFR of individual model galaxies is roughly proportional to (1+z)^2.2 for all the masses with a normalization factor that depends on mass as Ms^0.1, i.e more massive galaxies have slightly larger SSFRs, contrary to the observed strong SSFR-DS trend. For the re-accretion cases, the dependence on z remains approximately the same as without re-infall, but the correlation on Ms even increases for most of the reasonable values of the model parameters. The comparison of models and observations in the SSFR-Ms plane at z~0 shows the divergent trend in SSFR as lower are the masses (upsizing vs downsizing). We explain why the models show the reported trends, and conclude that the SSFR-DS for low-mass galaxies poses a challenge for LCDM-based disc galaxy evolution models. (Abridged), Comment: 12 pages, 4 figures. To appear in MNRAS. Text improved after Referee reports

We derive the stellar-to-halo mass relations, SHMR, of local blue and red central galaxies separately, as well as the fraction of halos hosting blue/red central galaxies. We find that: 1) the SHMR of central galaxies is segregated by color, with blue centrals having a SHMR above the one of red centrals; at logMh~12, the Ms/Mh ratio of the blue centrals is ~0.05, which is ~1.7 times larger than the value of red centrals. 2) The intrinsic scatters of the SHMRs of red and blue centrals are ~0.14 and ~0.11dex, respectively. The intrinsic scatter of the average SHMR of all central galaxies changes from ~0.20dex to ~0.14dex in the 11.3, Comment: Accepted for publication in ApJ (20/Nov/2014). 23 pages, 16 figures. This version has substantial changes after Referee's report. Parts of Section 5 from our previous version will be publish in a follow-up paper

We use a sample of ~6000 galaxies detected by the Arecibo Legacy Fast ALFA (ALFALFA) 21cm survey, to measure the clustering properties of HI-selected galaxies. We find no convincing evidence for a dependence of clustering on the galactic atomic hydrogen (HI) mass, over the range M_HI ~ 10^{8.5} - 10^{10.5} M_sun. We show that previously reported results of weaker clustering for low-HI mass galaxies are probably due to finite-volume effects. In addition, we compare the clustering of ALFALFA galaxies with optically selected samples drawn from the Sloan Digital Sky Survey (SDSS). We find that HI-selected galaxies cluster more weakly than even relatively optically faint galaxies, when no color selection is applied. Conversely, when SDSS galaxies are split based on their color, we find that the correlation function of blue optical galaxies is practically indistinguishable from that of HI-selected galaxies. At the same time, SDSS galaxies with red colors are found to cluster significantly more than HI-selected galaxies, a fact that is evident in both the projected as well as the full two-dimensional correlation function. A cross-correlation analysis further reveals that gas-rich galaxies "avoid" being located within ~3 Mpc of optical galaxies with red colors. Next, we consider the clustering properties of halo samples selected from the Bolshoi LambdaCDM simulation. A comparison with the clustering of ALFALFA galaxies suggests that galactic HI mass is not tightly related to host halo mass, and that a sizable fraction of subhalos do not host HI galaxies. Lastly, we find that we can recover fairly well the correlation function of HI galaxies by just excluding halos with low spin parameter. This finding lends support to the hypothesis that halo spin plays a key role in determining the gas content of galaxies., Comment: Accepted to ApJ. 27 figures, 1 table; 50 pages in aastex (equivalent to 19 pages of emulateapj)