Stellar-to-halo Mass Relation Research Articles

Effectiveness of halo and galaxy properties in reducing the scatter in the stellar-to-halo mass relation

Abstract The stellar-to-halo mass relation (SHMR) is a fundamental relationship between galaxies and their host dark matter haloes. In this study, we examine the scatter in this relation for primary galaxies in the semi-analytic L-Galaxies model and two cosmological hydrodynamical simulations, EAGLE and TNG100-1. We find that in low-mass haloes, more massive galaxies tend to reside in haloes with higher concentration, earlier formation time, greater environmental density, earlier major mergers, and, to have older stellar populations, which is consistent with findings in various studies. Quantitative analysis reveals the varying significance of halo and galaxy properties in determining SHMR scatter across simulations and models. In EAGLE and TNG100-1, halo concentration and formation time primarily influence SHMR scatter for haloes with $M_{\rm h}<10^{12}{ \rm M_\odot }$, but the influence diminishes at high mass. Baryonic processes play a more significant role in LGal. For halos with $M_{\rm h} <10^{11}{ \rm M_\odot }$ and $10^{12}{ \rm M_\odot }<M_{\rm h}<10^{13}{ \rm M_\odot }$, the main drivers of scatter are galaxy SFR and age. In the $10^{11.5}{ \rm M_\odot }<M_{\rm h} <10^{12}{ \rm M_\odot }$ range, halo concentration and formation time are the primary factors. And for halos with $M_{\rm h} > 10^{13}{ \rm M_\odot }$, supermassive black hole mass becomes more important. Interestingly, it is found that AGN feedback may increase the amplitude of the scatter and decrease the dependence on halo properties at high masses.

COSMOS2020: Cosmic evolution of the stellar-to-halo mass relation for central and satellite galaxies up to z ∼ 5

We used the COSMOS2020 catalog to measure the stellar-to-halo mass relation (SHMR) divided by central and satellite galaxies from z = 0.2 to z = 5.5. Starting from accurate photometric redshifts, we measured the near-infrared selected two-point angular correlation and stellar mass functions in ten redshift bins. We used a phenomenological model that parametrizes the stellar-to-halo mass relation for central galaxies and the number of galaxies inside each halo to describe our observations. This model qualitatively reproduces our measurements and their dependence on the stellar mass threshold. Surprisingly, the mean halo occupation distribution only shows a mild evolution with redshift suggesting that galaxies occupy halos similarly throughout cosmic time. At each redshift, we measured the ratio of stellar mass to halo mass, M*/Mh, which shows the characteristic strong dependence of halo mass with a peak at Mhpeak ∼ 2 × 1012 M⊙. For the first time, using a joint modeling of clustering and abundances, we measured the evolution of Mhpeak from z = 0.2 to z = 5.5. Mhpeak increases gradually with redshift from log Mhpeak/M⊙ ∼ 12.1 at z ∼ 0.3 to log Mhpeak/M⊙ ∼ 12.3 at z ∼ 2, and up to log Mhpeak/M⊙ ∼ 12.9 at z ∼ 5. Similarly, the stellar mass peak M∗peak increases with redshift from log M∗peak/M⊙ ∼ 10.5 at z ∼ 0.3 to log M∗peak/M⊙ ∼ 10.9 at z ∼ 3. The SHMR ratio at the peak halo mass remains almost constant with redshift. These results are in accordance with the scenario in which the peak of star-formation efficiency moves toward more massive halos at higher redshifts. We also measured the fraction of satellites as a function of stellar mass and redshift. For all stellar mass thresholds, the satellite fraction decreases at higher redshifts. At a given redshift, there is a higher fraction of low-mass satellites and this fraction reaches a plateau at ∼25% at z ∼ 1. The satellite contribution to the total stellar mass budget in halos becomes more important than that of the central at halo masses of about Mh > 1013 M⊙ and always stays below the peak, indicating that quenching mechanisms are present in massive halos that keep the star-formation efficiency low. Finally, we compared our results with three hydrodynamical simulations: HORIZON-AGN, TNG100 of the ILLUSTRISTNG project, and EAGLE. We find that the most significant discrepancy is at the high-mass end, where the simulations generally show that satellites have a higher contribution to the total stellar mass budget than the observations. This, together with the finding that the fraction of satellites is higher in the simulations, indicates that the feedback mechanisms acting in both group- and cluster-scale halos appear to be less efficient in quenching the mass assembly of satellites – and that quenching occurs much later in the simulations.

Scatter in the satellite galaxy SHMR: fitting functions, scaling relations, and physical processes from the IllustrisTNG simulation

ABSTRACT The connection between galaxies and their dark matter haloes is often described with the stellar-to-halo mass relation (SHMR). Satellite galaxies in clusters follow an SHMR distinct from central galaxies because of the environmental processes that they are subject to, and the variety of accretion histories leads to an important scatter in this relation. In this work, we use the suite of magnetohydrodynamical simulations IllustrisTNG to study the scatter in the satellite galaxy SHMR, and extract the parameters that can best allow to understand it. Active galaxies, that represent a very small fraction of cluster galaxies, follow a very different relation than their passive counterparts, mainly because they were accreted much more recently. For this latter population, we find that the distance to the cluster centre is a good predictor of variations in the SHMR, but some information on the galaxy orbital history, such as the distance of closest approach to the host centre, is an even better one, although it is in practice more difficult to measure. In addition, we found that galaxy compactness is also correlated with the SHMR, while the host cluster properties (mass and concentration, formation redshift, mass and size of BCG) do not play a significant role. We provide accurate fitting functions and scaling relations to the scientific community, useful to predict the subhalo mass given a set of observable parameters. Finally, we connect the scatter in the SHMR to the physical processes affecting galaxies in clusters, and how they impact the different satellite subpopulations.

The effects of self-interacting dark matter on the stripping of galaxies that fall into clusters

ABSTRACT We use the Cluster-EAGLE (c-eagle) hydrodynamical simulations to investigate the effects of self-interacting dark matter (SIDM) on galaxies as they fall into clusters. We find that SIDM galaxies follow similar orbits to their cold dark matter (CDM) counterparts, but end up with ∼25 per cent less mass by the present day. One in three SIDM galaxies is entirely disrupted, compared to one in five CDM galaxies. However, the excess stripping will be harder to observe than suggested by previous DM-only simulations because the most stripped galaxies form cores and also lose stars: The most discriminating objects become unobservable. The best test will be to measure the stellar-to-halo mass relation (SHMR) for galaxies with stellar mass $10^{10}\!-\!10^{11}\, \mathrm{M}_{\odot }$. This is 8 times higher in a cluster than in the field for a CDM universe, but 13 times higher for an SIDM universe. Given intrinsic scatter in the SHMR, these models could be distinguished with noise-free galaxy–galaxy strong lensing of ∼32 cluster galaxies.

Dynamical evidence for a morphology-dependent relation between the stellar and halo masses of galaxies

We derive the stellar-to-halo mass relation (SHMR), namely f⋆ ∝ M⋆/Mh versus M⋆ and Mh, for early-type galaxies from their near-infrared luminosities (for M⋆) and the position-velocity distributions of their globular cluster systems (for Mh). Our individual estimates of Mh are based on fitting a flexible dynamical model with a distribution function expressed in terms of action-angle variables and imposing a prior on Mh from the correlation between halo concentration and mass in the standard Λ cold dark matter (ΛCDM) cosmology. We find that the SHMR for early-type galaxies declines with mass beyond a peak at M⋆ ∼ 5 × 1010 M⊙ and Mh ∼ 1 × 1012 M⊙ (near the mass of the Milky Way). This result is consistent with the standard SHMR derived by abundance matching for the general population of galaxies, and also with previous, less robust derivations of the SHMR for early-type galaxies. However, it contrasts sharply with the monotonically rising SHMR for late-type galaxies derived from extended HI rotation curves and the same ΛCDM prior on Mh that we adopt for early-type galaxies. We show that the SHMR for massive galaxies varies more or less continuously with disc fraction and Hubble type between these rising and falling branches. We also show that the different SHMRs for late-type and early-type galaxies are consistent with the similar scaling relations between their stellar velocities and masses (the Tully–Fisher and the Faber–Jackson relations). As we demonstrate explicitly, differences in the relations between the stellar and halo virial velocities account for the similarity of the scaling relations. We argue that all these empirical findings are natural consequences of a picture in which galactic discs are built mainly by relatively smooth and gradual inflow, regulated by feedback from young stars, while galactic spheroids are built by a combination of merging, black-hole fuelling, and feedback from active galactic nuclei.

Shape noise and dispersion in precision weak lensing

ABSTRACT We analyse the first measurements from precision weak lensing (PWL): a new methodology for measuring individual galaxy–galaxy weak lensing through velocity information. Our goal is to understand the observed shear distribution from PWL, which is broader than can be explained by the statistical measurement errors. We identify two possible sources of scatter to explain the observed distribution: a shape noise term associated with the underlying assumption of circular stable rotation, and an astrophysical signal consistent with a lognormal dispersion around the stellar-to-halo mass relation (SHMR). We have modelled the observed distribution as the combination of these two factors and quantified their most likely values given our data. For the current sample, we measure an effective shape noise of σγ = 0.024 ± 0.007, highlighting the low noise impact of the method and positioning PWL as ∼10 times more precise than conventional weak lensing. We also measure an average dispersion in shears of $\xi _\gamma = 0.53^{+0.26}_{-0.28}$ dex over the range of 8.5 < log M⋆ < 11. This measurement is higher than expected, which is suggestive of a relatively high dispersion in halo mass and/or profile.

The distinct stellar-to-halo mass relations of satellite and central galaxies: insights from the IllustrisTNG simulations

ABSTRACT We study the stellar-to-halo mass relation (SHMR) for central and satellite galaxies with total dynamical masses above $10^{10.5}\, \rm {M}_\odot$ using the suite of cosmological magnetohydrodynamical simulations IllustrisTNG. In particular, we quantify environmental effects on satellite populations from TNG50, TNG100, and TNG300 located within the virial radius of group- and cluster-like hosts with total masses of $10^{12\!-\!15.2}\, \rm {M}_\odot$. At fixed stellar mass, the satellite SHMR exhibits a distinct shift towards lower dynamical mass compared to the SHMR of centrals. Conversely, at fixed dynamical mass, satellite galaxies appear to have larger stellar-to-total mass fractions than centrals by up to a factor of a few. The systematic deviation from the central SHMR is larger for satellites in more massive hosts, at smaller cluster-centric distances, with earlier infall times, and that inhabits higher local density environments; moreover, it is in place already at early times (z ≲ 2). Systematic environmental effects might contribute to the perceived galaxy-to-galaxy variation in the measured SHMR when galaxies cannot be separated into satellites and centrals. The SHMR of satellites exhibits a larger scatter than centrals (by up to ∼0.8 dex), over the whole range of dynamical mass. The shift of the satellite SHMR results mostly from tidal stripping of their dark matter, which affects satellites in an outside-in fashion: The departure of the satellite SHMR from the centrals’ relation diminishes for measurements of dynamical mass in progressively smaller apertures. Finally, we provide a family of fitting functions for the SHMR predicted by IllustrisTNG.

From lenticulars to blue compact dwarfs: the stellar mass fraction is regulated by disc gravitational instability

ABSTRACT The stellar-to-halo mass relation (SHMR) is not only one of the main sources of information we have on the connection between galaxies and their dark matter haloes, but also an important indicator of the performance of galaxy formation models. Here, we use one of the largest sample of galaxies with both high-quality rotation curves and near-infrared surface photometry, and perform a detailed comparative analysis of the SHMR. Our analysis shows that there are significant statistical differences between popular forms of the SHMR, and illustrates the predictive power of a new physically motivated scaling relation, which connects the stellar mass fraction (M⋆/Mh) to the stellar specific angular momentum (j⋆) and the stellar radial velocity dispersion (σ⋆) via disc gravitational instability. Making use of such a relation, we demonstrate (i) how challenging it is to reproduce the efficiency of galaxy formation even for state-of-the-art cosmological hydrodynamical simulations, and (ii) that the evolution of the stellar mass fraction is regulated by disc gravitational instability: when M⋆/Mh varies, j⋆ and σ⋆ also vary as predicted by our scaling relation, thus erasing the memory of such evolution. This implies that the process of disc gravitational instability is intriguingly uniform across disc galaxies of all morphological types: from lenticulars to blue compact dwarfs. In particular, the cosmic variance of Toomre’s Q is 0.2 dex, a universal value for both stars and atomic gas.

Stellar and weak lensing profiles of massive galaxies in the Hyper-Suprime Cam survey and in hydrodynamic simulations

ABSTRACT We perform a consistent comparison of the mass and mass profiles of massive (M⋆ > 1011.4 M⊙) central galaxies at z ∼ 0.4 from deep Hyper Suprime-Cam (HSC) observations and from the Illustris, TNG100, and Ponos simulations. Weak lensing measurements from HSC enable measurements at fixed halo mass and provide constraints on the strength and impact of feedback at different halo mass scales. We compare the stellar mass function (SMF) and the Stellar-to-Halo Mass Relation (SHMR) at various radii and show that the radius at which the comparison is performed is important. In general, Illustris and TNG100 display steeper values of α where $M_{\star } \propto M_{\rm vir}^{\alpha }$. These differences are more pronounced for Illustris than for TNG100 and in the inner rather than outer regions of galaxies. Differences in the inner regions may suggest that TNG100 is too efficient at quenching in situ star formation at Mvir ≃ 1013 M⊙ but not efficient enough at Mvir ≃ 1014 M⊙. The outer stellar masses are in excellent agreement with our observations at Mvir ≃ 1013 M⊙, but both Illustris and TNG100 display excess outer mass as Mvir ≃ 1014 M⊙ (by ∼0.25 and ∼0.12 dex, respectively). We argue that reducing stellar growth at early times in $M_\star \sim 10^{9-10} \, \mathrm{M}_{\odot }$ galaxies would help to prevent excess ex-situ growth at this mass scale. The Ponos simulations do not implement AGN feedback and display an excess mass of ∼0.5 dex at r < 30 kpc compared to HSC which is indicative of overcooling and excess star formation in the central regions. The comparison of the inner profiles of Ponos and HSC suggests that the physical scale over which the central AGN limits star formation is r ≲ 20 kpc. Joint comparisons between weak lensing and galaxy stellar profiles are a direct test of whether simulations build and deposit galaxy mass in the correct dark matter haloes and thereby provide powerful constraints on the physics of feedback and galaxy growth. Our galaxy and weak lensing profiles are publicly available to facilitate comparisons with other simulations.

The dependence of the galaxy stellar-to-halo mass relation on galaxy morphology

ABSTRACT We investigate the dependence of the local galaxy stellar-to-halo mass relation (SHMR) on galaxy morphology. We use data from the Sloan Digital Sky Survey (SDSS) data release 7 with morphological classifications from Galaxy Zoo, and compare with the EAGLE cosmological simulation. At fixed halo mass in the mass range $10^{11.7}\!-\!10^{12.9}\, {\rm M_{\odot }}$, the median stellar masses of SDSS disc galaxies are up to a factor of 1.4 higher than the median masses of their elliptical counterparts. However, when we switch from the stellar masses from Kauffmann et al. to those calculated by Chang et al. or Brinchmann et al., the median SHMR from discs and ellipticals coincides in this mass range. For halo masses larger than $10^{13}\, {\rm M_{\odot }}$, discs are less massive than ellipticals in same-mass haloes, regardless of whose stellar mass estimates we use. However, we find that for these high halo masses the results for discs may be affected by central/satellite misclassifications. The EAGLE simulation predicts that discs are up to a factor of 1.5 more massive than elliptical galaxies residing in same-mass haloes less massive than $10^{13}\, {\rm M_{\odot }}$, in agreement with the Kauffmann et al. data. Haloes with masses between 1011.5 and $10^{12}\, {\rm M_{\odot }}$, which host disc galaxies, were assembled earlier than those hosting ellipticals. This suggests that the discs are more massive because they had more time for gas accretion and star formation. In $10^{12}\!-\!10^{12.5}\, {\rm M_{\odot }}$ haloes, the central black holes in elliptical galaxies grew faster and became more massive than their counterparts in disc galaxies. This suggests that in this halo mass range the ellipticals are less massive because active galactic nucleus feedback ejected more of the halo’s gas reservoir, reducing star formation, and suppressing the (re)growth of stellar discs.

GAMA + KiDS: empirical correlations between halo mass and other galaxy properties near the knee of the stellar-to-halo mass relation

ABSTRACT We use KiDS weak lensing data to measure variations in mean halo mass as a function of several key galaxy properties (namely stellar colour, specific star formation rate, Sérsic index, and effective radius) for a volume-limited sample of GAMA galaxies in a narrow stellar mass range [M* ∼ (2–5) × 1010 M⊙]. This mass range is particularly interesting, inasmuch as it is where bimodalities in galaxy properties are most pronounced, and near to the break in both the galaxy stellar mass function and the stellar-to-halo mass relation (SHMR). In this narrow mass range, we find that both size and Sérsic index are better predictors of halo mass than either colour or SSFR, with the data showing a slight preference for Sérsic index. In other words, we find that mean halo mass is more tightly correlated with galaxy structure than either past star formation history or current star formation rate. Our results lead to an approximate lower bound on the dispersion in halo masses among log M* ≈ 10.5 galaxies: We find that the dispersion is ≳0.3 dex. This would imply either that offsets from the mean SHMR are closely coupled to size/structure or that the dispersion in the SHMR is larger than what past results have suggested. Our results thus provide new empirical constraints on the relationship between stellar and halo mass assembly at this particularly interesting mass range.

Abundance matching tested on small scales with galaxy dynamics

Abstract We present a comprehensive test of the relation between stellar and total masses in galaxies as predicted by popular models based on abundance matching (AM) techniques. We use the ‘Spectroscopy and H-band Imaging of Virgo cluster galaxies’ (SHIVir) survey with photometric and dynamical profiles for 190 Virgo cluster galaxies to establish a relation between the stellar and dynamical masses measured within the isophotal radius r23.5. Various dark matter and galaxy scaling relations are combined with results from the NIHAO (Numerical Investigation of Hundred Astrophysical Objects) suite of hydrodynamical simulations to recast AM predictions in terms of these observed quantities. Our results are quite insensitive to the exact choice of dark matter profile and halo response to baryon collapse. We find that theoretical models reproduce the slope and normalization of the observed stellar-to-halo mass relation (SHMR) over more than three orders of magnitude in stellar mass (108 < M*/M⊙ < 2 × 1011). However, the scatter of the observed SHMR exceeds that of AM predictions by a factor of ∼5. For systems with stellar masses exceeding 5 × 1010 M⊙, AM overpredicts the observed stellar masses for a given dynamical mass. The latter offset may support previous indications of a different stellar initial mass function in these massive galaxies. Overall, our results support the validity of AM predictions on a wide dynamical range.

The stellar-to-halo mass relation over the past 12 Gyr

Aims. Understanding the link between the galaxy properties and the dark matter halos they reside in and their coevolution is a powerful tool for constraining the processes related to galaxy formation. In particular, the stellar-to-halo mass relation (SHMR) and its evolution throughout the history of the Universe provides insights on galaxy formation models and allows us to assign galaxy masses to halos in N-body dark matter simulations. To address these questions, we determine the SHMR throughout the entire cosmic history from z ∼ 4 to the present. Methods. We used a statistical approach to link the observed galaxy stellar mass functions on the COSMOS field to dark matter halo mass functions up to z ∼ 4 from the ΛCDM DUSTGRAIN-pathfinder simulation, which is complete for Mh > 1012.5 M⊙, and extended this to lower masses with a theoretical parameterization. We propose an empirical model to describe the evolution of the SHMR as a function of redshift (either in the presence or absence of a scatter in stellar mass at fixed halo mass), and compare the results with several literature works and semianalytic models of galaxy formation. We also tested the reliability of our results by comparing them to observed galaxy stellar mass functions and to clustering measurements. Results. We derive the SHMR from z = 0 to z = 4, and model its empirical evolution with redshift. We find that M*/Mh is always lower than ∼0.05 and depends both on redshift and halo mass, with a bell shape that peaks at Mh ∼ 1012 M⊙. Assuming a constant cosmic baryon fraction, we calculate the star-formation efficiency of galaxies and find that it is generally low; its peak increases with cosmic time from ∼30% at z ∼ 4 to ∼35% at z ∼ 0. Moreover, the star formation efficiency increases for increasing redshifts at masses higher than the peak of the SHMR, while the trend is reversed for masses lower than the peak. This indicates that massive galaxies (i.e., galaxies hosted at halo masses higher than the SHMR peak) formed with a higher efficiency at higher redshifts (i.e., downsizing effect) and vice versa for low-mass halos. We find a large scatter in results from semianalytic models, with a difference of up to a factor ∼8 compared to our results, and an opposite evolutionary trend at high halo masses. By comparing our results with those in the literature, we find that while at z ∼ 0 all results agree well (within a factor of ∼3), at z > 0 many differences emerge. This suggests that observational and theoretical work still needs to be done. Our results agree well (within ∼10%) with observed stellar mass functions (out to z = 4) and observed clustering of massive galaxies (M* > 1011 M⊙ from z ∼ 0.5 to z ∼ 1.1) in the two-halo regime.

Study of gravitational fields and globular cluster systems of early-type galaxies

Context.Gravitational fields at the outskirts of early-type galaxies (ETGs) are difficult to constrain observationally. It thus remains poorly explored how well the ΛCDM and MOND hypotheses agree with ETGs.Aims.The dearth of studies on this topic motivated us to gather a large sample of ETGs and examine homogeneously which dark matter halos they occupy, whether the halos follow the theoretically predicted stellar-to-halo mass relation (SHMR) and the halo mass-concentration relation (HMCR), whether ETGs obey MOND and the radial acceleration relation (RAR) observed for late-type galaxies (LTGs), and finally whether ΛCDM or MOND perform better in ETGs.Methods.We employed Jeans analysis of radial velocities of globular clusters (GCs). We analysed nearly all ETGs having more than about 100 archival GC radial velocity measurements available. The GC systems of our 17 ETGs extend mostly over ten effective radii. A ΛCDM simulation of GC formation helped us to interpret the results.Results.Successful ΛCDM fits are found for all galaxies, but compared to the theoretical HMCR and SHMR, the best-fit halos usually have concentrations that are too low and stellar masses that are too high for their masses. This might be because of tidal stripping of the halos or because ETGs and LTGs occupy different halos. Most galaxies can be fitted by the MOND models successfully as well, but for some of the galaxies, especially those in centers of galaxy clusters, the observed GC velocity dispersions are too high. This might be a manifestation of the additional dark matter that MOND requires in galaxy clusters. Additionally, we find many signs that the GC systems were perturbed by galaxy interactions. Formal statistical criteria prefer the best-fit ΛCDM models over the MOND models, but this might be due to the higher flexibility of the ΛCDM models. The MOND approach can predict the GC velocity dispersion profiles better.

Galaxy spin as a formation probe: the stellar-to-halo specific angular momentum relation

We derive the stellar-to-halo specific angular momentum relation (SHSAMR) of galaxies at $z=0$ by combining i) the standard $\Lambda$CDM tidal torque theory ii) the observed relation between stellar mass and specific angular momentum (Fall relation) and iii) various determinations of the stellar-to-halo mass relation (SHMR). We find that the ratio $f_j = j_\ast/j_{\rm h}$ of the specific angular momentum of stars to that of the dark matter i) varies with mass as a double power-law, ii) it always has a peak in the mass range explored and iii) it is $3-5$ times larger for spirals than for ellipticals. The results have some dependence on the adopted SHMR and we provide fitting formulae in each case. For any choice of the SHMR, the peak of $f_j$ occurs at the same mass where the stellar-to-halo mass ratio $f_\ast = M_\ast/M_{\rm h}$ has a maximum. This is mostly driven by the straightness and tightness of the Fall relation, which requires $f_j$ and $f_\ast$ to be correlated with each other roughly as $f_j\propto f_\ast^{2/3}$, as expected if the outer and more angular momentum rich parts of a halo failed to accrete onto the central galaxy and form stars (biased collapse). We also confirm that the difference in the angular momentum of spirals and ellipticals at a given mass is too large to be ascribed only to different spins of the parent dark-matter haloes (spin bias).

Constraining the galaxy–halo connection over the last 13.3 Gyr: star formation histories, galaxy mergers and structural properties

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.

Is main-sequence galaxy star formation controlled by halo mass accretion?

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.

DARK MATTER HALO MODELS OF STELLAR MASS-DEPENDENT GALAXY CLUSTERING IN PRIMUS+DEEP2 AT 0.2 &lt;z&lt; 1.2

We utilize $\Lambda$CDM halo occupation models of galaxy clustering to investigate the evolving stellar mass dependent clustering of galaxies in the PRIsm MUlti-object Survey (PRIMUS) and DEEP2 Redshift Survey over the past eight billion years of cosmic time, between $0.2<z<1.2$. These clustering measurements provide new constraints on the connections between dark matter halo properties and galaxy properties in the context of the evolving large-scale structure of the universe. Using both an analytic model and a set of mock galaxy catalogs, we find a strong correlation between central galaxy stellar mass and dark matter halo mass over the range $M_\mathrm{halo}\sim10^{11}$-$10^{13}~h^{-1}M_\odot$, approximately consistent with previous observations and theoretical predictions. However, the stellar-to-halo mass relation (SHMR) and the mass scale where star formation efficiency reaches a maximum appear to evolve more strongly than predicted by other models, including models based primarily on abundance-matching constraints. We find that the fraction of satellite galaxies in haloes of a given mass decreases significantly from $z\sim0.5$ to $z\sim0.9$, partly due to the fact that haloes at fixed mass are rarer at higher redshift and have lower abundances. We also find that the $M_1/M_\mathrm{min}$ ratio, a model parameter that quantifies the critical mass above which haloes host at least one satellite, decreases from $\approx20$ at $z\sim0$ to $\approx13$ at $z\sim0.9$. Considering the evolution of the subhalo mass function vis-\`{a}-vis satellite abundances, this trend has implications for relations between satellite galaxies and halo substructures and for intracluster mass, which we argue has grown due to stripped and disrupted satellites between $z\sim0.9$ and $z\sim0.5$.

The dark matter haloes of moderate luminosity X-ray AGN as determined from weak gravitational lensing and host stellar masses

Understanding the relationship between galaxies hosting active galactic nuclei (AGN) and the dark matter halos in which they reside is key to constraining how black-hole fueling is triggered and regulated. Previous efforts have relied on simple halo mass estimates inferred from clustering, weak gravitational lensing, or halo occupation distribution modeling. In practice, these approaches remain uncertain because AGN, no matter how they are identified, potentially live a wide range of halo masses with an occupation function whose general shape and normalization are poorly known. In this work, we show that better constraints can be achieved through a rigorous comparison of the clustering, lensing, and cross-correlation signals of AGN hosts to a fiducial stellar-to-halo mass relation (SHMR) derived for all galaxies. Our technique exploits the fact that the global SHMR can be measured with much higher accuracy than any statistic derived from AGN samples alone. Using 382 moderate luminosity X-ray AGN at z<1 from the COSMOS field, we report the first measurements of weak gravitational lensing from an X-ray selected sample. Comparing this signal to predictions from the global SHMR, we find that, contrary to previous results, most X-ray AGN do not live in medium size groups ---nearly half reside in relatively low mass halos with Mh~10^12.5 Msun. The AGN occupation function is well described by the same form derived for all galaxies but with a lower normalization---the fraction of halos with AGN in our sample is a few percent. By highlighting the relatively "normal" way in which moderate luminosity X-ray AGN hosts occupy halos, our results suggest that the environmental signature of distinct fueling modes for luminous QSOs compared to moderate luminosity X-ray AGN is less obvious than previously claimed.

THE STELLAR-TO-HALO MASS RELATION FOR LOCAL GROUP GALAXIES

We contend that a single power law halo mass distribution is appropriate for direct matching to the stellar masses of observed Local Group dwarf galaxies, allowing the determination of the slope of the stellar mass-halo mass relation for low mass galaxies. Errors in halo masses are well defined as the Poisson noise of simulated local group realisations, which we determine using constrained local universe simulations (CLUES). For the stellar mass range 10$^7$<M*<10$^8$M$_\odot$, for which we likely have a complete census of observed galaxies, we find that the stellar mass-halo mass relation follows a power law with slope of 3.1, significantly steeper than most values in the literature. The steep relation between stellar and halo masses indicates that Local Group dwarf galaxies are hosted by dark matter halos with a small range of mass. Our methodology is robust down to the stellar mass to which the census of observed Local Group galaxies is complete, but the significant uncertainty in the currently measured slope of the stellar-to halo mass relation will decrease dramatically if the Local Group completeness limit was $10^{6.5}$M$\odot$ or below, highlighting the importance of pushing such limit to lower masses and larger volumes.