587 research outputs found
Constraints on the relationship between stellar mass and halo mass at low and high redshift
We use a statistical approach to determine the relationship between the
stellar masses of galaxies and the masses of the dark matter halos in which
they reside. We obtain a parameterized stellar-to-halo mass (SHM) relation by
populating halos and subhalos in an N-body simulation with galaxies and
requiring that the observed stellar mass function be reproduced. We find good
agreement with constraints from galaxy-galaxy lensing and predictions of
semi-analytic models. Using this mapping, and the positions of the halos and
subhalos obtained from the simulation, we find that our model predictions for
the galaxy two-point correlation function (CF) as a function of stellar mass
are in excellent agreement with the observed clustering properties in the SDSS
at z=0. We show that the clustering data do not provide additional strong
constraints on the SHM function and conclude that our model can therefore
predict clustering as a function of stellar mass. We compute the conditional
mass function, which yields the average number of galaxies with stellar masses
in the range [m, m+dm] that reside in a halo of mass M. We study the redshift
dependence of the SHM relation and show that, for low mass halos, the SHM ratio
is lower at higher redshift. The derived SHM relation is used to predict the
stellar mass dependent galaxy CF and bias at high redshift. Our model predicts
that not only are massive galaxies more biased than low mass ones at all
redshifts, but the bias increases more rapidly with increasing redshift for
massive galaxies than for low mass ones. We present convenient fitting
functions for the SHM relation as a function of redshift, the conditional mass
function, and the bias as a function of stellar mass and redshift.Comment: 21 pages, 17 figures, discussion enlarged, one more figure, updated
references, accepted for publication in Ap
The Stellar Mass Components of Galaxies: Comparing Semi-Analytical Models with Observation
We compare the stellar masses of central and satellite galaxies predicted by
three independent semianalytical models with observational results obtained
from a large galaxy group catalogue constructed from the Sloan Digital Sky
Survey. In particular, we compare the stellar mass functions of centrals and
satellites, the relation between total stellar mass and halo mass, and the
conditional stellar mass functions, which specify the average number of
galaxies of stellar mass M_* that reside in a halo of mass M_h. The
semi-analytical models only predict the correct stellar masses of central
galaxies within a limited mass range and all models fail to reproduce the sharp
decline of stellar mass with decreasing halo mass observed at the low mass end.
In addition, all models over-predict the number of satellite galaxies by
roughly a factor of two. The predicted stellar mass in satellite galaxies can
be made to match the data by assuming that a significant fraction of satellite
galaxies are tidally stripped and disrupted, giving rise to a population of
intra-cluster stars in their host halos. However, the amount of intra-cluster
stars thus predicted is too large compared to observation. This suggests that
current galaxy formation models still have serious problems in modeling star
formation in low-mass halos.Comment: 12 pages, 6 figures, accepted for publication in Ap
Understanding the PSCz Galaxy Power Spectrum with N-body Simulations
By comparing the PSCz galaxy power spectrum with the results of nested pure
dark matter N-body simulations, we try to understand how infrared-selected
galaxies populate dark-matter haloes, paying special attention to the method of
halo identification in the simulations. We thus test the hypothesis that
baryonic physics negligibly affects the distribution of galaxies down to the
smallest scales yet observed. We are successful in reproducing the PSCz power
spectrum on scales < ~40 h/Mpc, near our resolution limit, by imposing a
central density cut-off on simulated haloes, which gives a rough minimum mass
and circular velocity of haloes in which PSCz galaxies formed.Comment: 12 pages, 16 figures (one added), conforms to version in MNRA
A lightcone catalogue from the Millennium-XXL simulation
Future galaxy surveys require realistic mock catalogues to understand and quantify systematics in order to make precise cosmological measurements. We present a halo lightcone catalogue and halo occupation distribution (HOD) galaxy catalogue built using the Millennium-XXL simulation. The halo catalogue covers the full sky, extending to z = 2.2 with a mass resolution of ∼1011 h−1 M⊙. We use this to build a galaxy catalogue, which has an r-band magnitude limit of r < 20.0, with a median redshift of z ∼ 0.2. A Monte Carlo HOD method is used to assign galaxies to the halo lightcone catalogue, and we evolve the HODs to reproduce a target luminosity function; by construction, the luminosity function of galaxies in the mock is in agreement with the Sloan Digital Sky Survey (SDSS) at low redshifts and the Galaxy and Mass Assembly (GAMA) survey at high redshifts. A Monte Carlo method is used to assign a 0.1(g − r) colour to each galaxy, and the colour distribution of galaxies at different redshifts agrees with measurements from GAMA. The clustering of galaxies in the mock for galaxies in different magnitude and redshift bins is in good agreement with measurements from SDSS and GAMA, and the colour-dependent clustering is in reasonable agreement. We show that the baryon acoustic oscillation can be measured in the mock catalogue, and the redshift-space distortions are in agreement with measurements from SDSS illustrating that this catalogue will be useful for upcoming surveys
Mapping the Dark Matter From UV Light at High Redshift: An Empirical Approach to Understand Galaxy Statistics
We present a simple formalism to interpret two galaxy statistics, the UV
luminosity function and two-point correlation functions for star-forming
galaxies at z~4, 5, 6 in the context of LCDM cosmology. Both statistics are the
result of how star formation takes place in DM halos, and thus are used to
constrain how UV light depends on halo properties such as mass. The two
measures were taken from the GOODS data, thus ideal for joint analysis. The two
physical quantities we explore are the SF duty cycle, and the range of L_UV
that a halo of mass M can have (mean and variance). The former addresses the
typical duration of SF activity in halos while the latter addresses the
averaged SF history and regularity of gas inflow into these systems. We explore
various physical models consistent with data, and find the following: 1) the
typical duration of SF observed in the data is <0.4 Gyr (1 sig), 2) the
inferred scaling law between L_UV and halo mass M from the observed slope of
the LFs is roughly linear at all redshifts, and 3) L_UV for a fixed halo mass
decreases with time, implying that the SF efficiency (after dust extinction) is
higher at earlier times. We explore several physical scenarios relating star
formation to halo mass, but find that these scenarios are indistinguishable due
to the limited range of halo mass probed by our data. In order to discriminate
between different scenarios, we discuss constraining the bright-faint galaxy
cross-correlation functions and luminosity-dependence of galaxy bias.
(Abridged)Comment: 24 pages, 16 figures: matches published version -- Astrophysical
Journal 695 (2009) 368-39
Constraining halo occupation properties of X-ray AGNs using clustering of Chandra sources in the Bootes survey region
We present one of the most precise measurement to date of the spatial
clustering of X-ray selected AGNs using a sample derived from the Chandra X-ray
Observatory survey in the Bootes field. The real-space two-point correlation
function over a redshift interval from z=0.17 to z~3 is well described by the
power law, xi(r)=(r/r0)^-gamma, for comoving separations r<~20h^-1 Mpc. We find
gamma=1.84+-0.12 and r0 consistent with no redshift trend within the sample
(varying between r0=5.5+-0.6 h^-1 Mpc for =0.37 and r0=6.9+-1.0 h^-1 Mpc for
=1.28). Further, we are able to measure the projections of the two-point
correlation function both on the sky plane and in the line of sight. We use
these measurements to show that the Chandra/Bootes AGNs are predominantly
located at the centers of dark matter halos with the circular velocity Vmax>320
km/s or M_200 > 4.1e12 h^-1 Msun, and tend to avoid satellite galaxies in halos
of this or higher mass. The halo occupation properties inferred from the
clustering properties of Chandra/Bootes AGNs --- the mass scale of the parent
dark matter halos, the lack of significant redshift evolution of the clustering
length, and the low satellite fraction --- are broadly consistent with the
Hopkins et al. scenario of quasar activity triggered by mergers of
similarly-sized galaxies.Comment: Accepted to ApJ. The revision matches the accepted version. The most
significant changes include the recalculation of uncertainties using mock
catalogs and explicit comparison with the AGN HOD studies based on projected
correlation function, w(rp
A galaxy-halo model of large-scale structure
We present a new, galaxy-halo model of large-scale structure, in which the
galaxies entering a given sample are the fundamental objects. Haloes attach to
galaxies, in contrast to the standard halo model, in which galaxies attach to
haloes. The galaxy-halo model pertains mainly to the relationships between the
power spectra of galaxies and mass, and their cross-power spectrum. With
surprisingly little input, an intuition-aiding approximation to the
galaxy-matter cross-correlation coefficient R(k) emerges, in terms of the halo
mass dispersion. This approximation seems valid to mildly non-linear scales (k
< ~3 h/Mpc), allowing measurement of the bias and the matter power spectrum
from measurements of the galaxy and galaxy-matter power spectra (or correlation
functions). This is especially relevant given the recent advances in precision
in measurements of the galaxy-matter correlation function from weak
gravitational lensing. The galaxy-halo model also addresses the issue of
interpreting the galaxy-matter correlation function as an average halo density
profile, and provides a simple description of galaxy bias as a function of
scale.Comment: 13 pages, 9 figures, submitted to MNRAS. Minor changes, suggested by
refere
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