191 research outputs found
Physical Correlations of the Scatter between Galaxy Mass, Stellar Content, and Halo Mass
We use the UniverseMachine to analyze the source of scatter between the
central galaxy mass, the total stellar mass in the halo, and the dark matter
halo mass. We also propose a new halo mass estimator, the cen+N mass: the sum
of the stellar mass of the central and the N most massive satellites. We show
that, when real space positions are perfectly known, the cen+N mass has scatter
competitive with that of richness-based estimators. However, in redshift space,
the cen+N mass suffers less from projection effects in the UniverseMachine
model. The cen+N mass is therefore a viable low scatter halo mass estimator,
and should be considered an important tool to constrain cosmology with upcoming
spectroscopic data from DESI. We analyze the scatter in stellar mass at fixed
halo mass and show that the total stellar mass in a halo is uncorrelated with
secondary halo properties, but that the central stellar mass is a function of
both halo mass and halo age. This is because central galaxies in older halos
have had more time to grow via accretion. If the UniverseMachine model is
correct, accurate galaxy-halo modeling of mass selected samples therefore needs
to consider halo age in addition to mass.Comment: 13 pages, 11 figures, submitted to MNRA
The Stripe 82 Massive Galaxy Project III: A Lack of Growth Among Massive Galaxies
The average stellar mass (Mstar) of high-mass galaxies (Mstar > 3e11 Msun) is
expected to grow by ~30% since z~1, largely through ongoing mergers that are
also invoked to explain the observed increase in galaxy sizes. Direct evidence
for the corresponding growth in stellar mass has been elusive, however, in part
because the volumes sampled by previous redshift surveys have been too small to
yield reliable statistics. In this work, we make use of the Stripe 82 Massive
Galaxy Catalog to build a mass-limited sample of 41,770 galaxies (Mstar >
1.6e11) with optical to near-IR photometry and a large fraction (>55%) of
spectroscopic redshifts. Our sample spans 139 square degrees, significantly
larger than most previous efforts. After accounting for a number of potential
systematic errors, including the effects of Mstar scatter, we measure galaxy
stellar mass functions over 0.3 < z < 0.65 and detect no growth in the typical
Mstar of massive galaxies with an uncertainty of 9%. This confidence level is
dominated by uncertainties in the star formation history assumed for Mstar
estimates, although our inability to characterize low surface-brightness
outskirts may be the most important limitation of our study. Even among these
high-mass galaxies, we find evidence for differential evolution when splitting
the sample by recent star formation (SF) activity. While low-SF systems appear
to become completely passive, we find a mostly sub-dominant population of
galaxies with residual, but low rates of star formation (~1 Msun/yr) number
density does not evolve. Interestingly, these galaxies become more prominent at
higher Mstar, representing ~10% of all galaxies at Mstar ~ 1e12 Msun and
perhaps dominating at even larger masses.Comment: Accepted in Ap
A 2.5% measurement of the growth rate from small-scale redshift space clustering of SDSS-III CMASS galaxies
We perform the first fit to the anisotropic clustering of SDSS-III CMASS DR10
galaxies on scales of ~ 0.8 - 32 Mpc/h. A standard halo occupation distribution
model evaluated near the best fit Planck LCDM cosmology provides a good fit to
the observed anisotropic clustering, and implies a normalization for the
peculiar velocity field of M ~ 2 x 10^13 Msun/h halos of f*sigma8(z=0.57) =
0.450 +/- 0.011. Since this constraint includes both quasi-linear and
non-linear scales, it should severely constrain modified gravity models that
enhance pairwise infall velocities on these scales. Though model dependent, our
measurement represents a factor of 2.5 improvement in precision over the
analysis of DR11 on large scales, f*sigma8(z=0.57) = 0.447 +/- 0.028, and is
the tightest single constraint on the growth rate of cosmic structure to date.
Our measurement is consistent with the Planck LCDM prediction of 0.480 +/-
0.010 at the ~1.9 sigma level. Assuming a halo mass function evaluated at the
best fit Planck cosmology, we also find that 10% of CMASS galaxies are
satellites in halos of mass M ~ 6 x 10^13 Msun/h. While none of our tests and
model generalizations indicate systematic errors due to an insufficiently
detailed model of the galaxy-halo connection, the precision of these first
results warrant further investigation into the modeling uncertainties and
degeneracies with cosmological parameters.Comment: 24 pages, 20 figures, submitted to MNRAS. v2 is 27 pages, 23 figures,
accepted by MNRA
First measurement of the cross-correlation of CMB lensing and galaxy lensing
We measure the cross-correlation of cosmic microwave background (CMB) lensing convergence maps derived from Atacama Cosmology Telescope data with galaxy lensing convergence maps as measured by the Canada-France-Hawaii Telescope Stripe 82 Survey. The CMB-galaxy lensing cross power spectrum is measured for the first time with a significance of 4.2 sigma, which corresponds to a 12% constraint on the amplitude of density fluctuations at redshifts similar to 0.9. With upcoming improved lensing data, this novel type of measurement will become a powerful cosmological probe, providing a precise measurement of the mass distribution at intermediate redshifts and serving as a calibrator for systematic biases in weak lensing measurements
Individual Stellar Halos of Massive Galaxies Measured to 100 kpc at using Hyper Suprime-Cam
Massive galaxies display extended light profiles that can reach several
hundreds of kilo parsecs. These stellar halos provide a fossil record of galaxy
assembly histories. Using data that is both wide (~100 square degree) and deep
(i>28.5 mag/arcsec^2 in i-band), we present a systematic study of the stellar
halos of a sample of more than 3000 galaxies at 0.3 < z < 0.5 with . Our study is based on high-quality (0.6 arcsec
seeing) imaging data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program
(SSP), which enables us to individually estimate surface mass density profiles
to 100 kpc without stacking. As in previous work, we find that more massive
galaxies exhibit more extended outer profiles. When this extended light is not
properly accounted for as a result of shallow imaging or inadequate profile
modeling, the derived stellar mass function can be significantly underestimated
at the highest masses. Across our sample, the ellipticity of outer light
profiles increases substantially as we probe larger radii. We show for the
first time that these ellipticity gradients steepen dramatically as a function
of galaxy mass, but we detect no mass-dependence in outer color gradients. Our
results support the two-phase formation scenario for massive galaxies in which
outer envelopes are built up at late times from a series of merging events. We
provide surface mass surface mass density profiles in a convenient tabulated
format to facilitate comparisons with predictions from numerical simulations of
galaxy formation.Comment: Submitted to MNRAS; 23 pages, 8 figures, 2 appendix; Data will be
made available here: http://massivegalaxies.com/ once the paper is publishe
Can we use Weak Lensing to Measure Total Mass Profiles of Galaxies on 20 kiloparsec Scales?
Current constraints on dark matter density profiles from weak lensing are
typically limited to radial scales greater than 50-100 kpc. In this paper, we
explore the possibility of probing the very inner regions of galaxy/halo
density profiles by measuring stacked weak lensing on scales of only a few tens
of kpc. Our forecasts focus on scales smaller than the equality radius (Req)
where the stellar component and the dark matter component contribute equally to
the lensing signal. We compute the evolution of Req as a function of lens
stellar mass and redshift and show that Req=7-34 kpc for galaxies with the
stellar mass of 10^{9.5}-10^{11.5} solar masses. Unbiased shear measurements
will be challenging on these scales. We introduce a simple metric to quantify
how many source galaxies overlap with their neighbours and for which shear
measurements will be challenging. Rejecting source galaxies with close-by
companions results in about a 20 per cent decrease in the overall source
density. Despite this decrease, we show that Euclid and WFIRST will be able to
constrain galaxy/halo density profiles at Req with signal-to-noise ratio >20
for the stellar mass of >10^{10} solar masses. Weak lensing measurements at
Req, in combination with stellar kinematics on smaller scales, will be a
powerful means by which to constrain both the inner slope of the dark matter
density profile as well as the mass and redshift dependence of the stellar
initial mass function.Comment: 19 pages, 14 figures, 3 tables, submitted to MNRAS, included the
referee comment
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