823 research outputs found
The spectroscopically confirmed X-ray cluster at z=1.62 with a possible companion in the Subaru/XMM-Newton deep field
We report on a confirmed galaxy cluster at z=1.62. We discovered two
concentrations of galaxies at z~1.6 in the Subaru/XMM-Newton deep field based
on deep multi-band photometric data. We made a near-IR spectroscopic follow-up
observation of them and confirmed several massive galaxies at z=1.62. One of
the two is associated with an extended X-ray emission at 4.5 sigma on a scale
of 0'.5, which is typical of high-z clusters. The X-ray detection suggests that
it is a gravitationally bound system. The other one shows a hint of an X-ray
signal, but only at 1.5 sigma, and we obtained only one secure redshift at
z=1.62. We are not yet sure if this is a collapsed system. The possible twins
exhibit a clear red sequence at K<22 and seem to host relatively few number of
faint red galaxies. Massive red galaxies are likely old galaxies -- they have
colors consistent with the formation redshift of z_f=3 and a spectral fit of
the brightest confirmed member yields an age of 1.8_{-0.2}^{+0.1} Gyr with a
mass of 2.5_{-0.1}^{+0.2} x 10^11 M_solar. Our results show that it is feasible
to detect clusters at z>1.5 in X-rays and also to perform detailed analysis of
galaxies in them with the existing near-IR facilities on large telescopes.Comment: 5 figures, accepted for publication in ApJ Letters
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
A theoretical framework for combining techniques that probe the link between galaxies and dark matter
We develop a theoretical framework that combines measurements of
galaxy-galaxy lensing, galaxy clustering, and the galaxy stellar mass function
in a self-consistent manner. While considerable effort has been invested in
exploring each of these probes individually, attempts to combine them are still
in their infancy despite the potential of such combinations to elucidate the
galaxy-dark matter connection, to constrain cosmological parameters, and to
test the nature of gravity. In this paper, we focus on a theoretical model that
describes the galaxy-dark matter connection based on standard halo occupation
distribution techniques. Several key modifications enable us to extract
additional parameters that determine the stellar-to-halo mass relation and to
simultaneously fit data from multiple probes while allowing for independent
binning schemes for each probe. In a companion paper, we demonstrate that the
model presented here provides an excellent fit to galaxy-galaxy lensing, galaxy
clustering, and stellar mass functions measured in the COSMOS survey from z=0.2
to z=1.0. We construct mock catalogs from numerical simulations to investigate
the effects of sample variance and covariance on each of the three probes.
Finally, we analyze and discuss how trends in each of the three observables
impact the derived parameters of the model. In particular, we investigate the
various features of the observed galaxy stellar mass function (low-mass slope,
plateau, knee, and high-mass cut-off) and show how each feature is related to
the underlying relationship between stellar and halo mass. We demonstrate that
the observed plateau feature in the stellar mass function at Mstellar~2x10^10
Msun is due to the transition that occurs in the stellar-to-halo mass relation
at Mhalo ~ 10^12 Msun from a low-mass power-law regime to a sub-exponential
function at higher stellar mass.Comment: 21 pages. Accepted to Ap
Lensing without borders - I. A blind comparison of the amplitude of galaxy-galaxy lensing between independent imaging surveys
ArtÃculo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboración, si lo hubiereThis is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Monthly Notices of the Royal Astronomical Society 510.4 (2022): 6150-6189 is available online at: https://academic.oup.com/mnras/article-abstract/510/4/6150/6461104?redirectedFrom=fulltext#no-access-messageLensing without borders is a cross-survey collaboration created to assess the consistency of galaxy–galaxy lensing signals (ΔΣ) across different data sets and to carry out end-to-end tests of systematic errors. We perform a blind comparison of the amplitude of ΔΣ using lens samples from BOSS and six independent lensing surveys. We find good agreement between empirically estimated and reported systematic errors which agree to better than 2.3σ in four lens bins and three radial ranges. For lenses with zL > 0.43 and considering statistical errors, we detect a 3–4σ correlation between lensing amplitude and survey depth. This correlation could arise from the increasing impact at higher redshift of unrecognized galaxy blends on shear calibration and imperfections in photometric redshift calibration. At zL > 0.54, amplitudes may additionally correlate with foreground stellar density. The amplitude of these trends is within survey-defined systematic error budgets that are designed to include known shear and redshift calibration uncertainty. Using a fully empirical and conservative method, we do not find evidence for large unknown systematics. Systematic errors greater than 15 per cent (25 per cent) ruled out in three lens bins at 68 per cent (95 per cent) confidence at z < 0.54. Differences with respect to predictions based on clustering are observed to be at the 20–30 per cent level. Our results therefore suggest that lensing systematics alone are unlikely to fully explain the ‘lensing is low’ effect at z < 0.54. This analysis demonstrates the power of cross-survey comparisons and provides a promising path for identifying and reducing systematics in future lensing analyse
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