Combining clustering and abundances of galaxy clusters to test cosmology and primordial non-Gaussianity. (arXiv:1303.0287v1 [astro-ph.CO])

Combining clustering and abundances of galaxy clusters to test cosmology and primordial non-Gaussianity. (arXiv:1303.0287v1 [astro-ph.CO]):
We present the clustering of galaxy clusters as a useful addition to the
common set of cosmological observables. The clustering of clusters probes the
large-scale structure of the Universe, extending galaxy clustering analysis to
the high-peak, high-bias regime. Clustering of galaxy clusters complements the
traditional cluster number counts and observable-mass relation analyses,
significantly improving their constraining power by breaking existing
calibration degeneracies. We use the maxBCG galaxy clusters catalogue to
constrain cosmological parameters and cross-calibrate the mass-observable
relation, using cluster abundances in richness bins and weak-lensing mass
estimates. We then add the redshift-space power spectrum of the sample,
including an effective modelling of the weakly non-linear contribution and
allowing for an arbitrary photometric redshift smoothing. The inclusion of the
power spectrum data allows for an improved self-calibration of the scaling
relation. We find that the inclusion of the power spectrum typically brings a
~50% improvement in the errors on the fluctuation amplitude sigma_8 and the
matter density Omega_m. Finally, we apply this method to constrain models of
the early universe through the amount of primordial non-Gaussianity of the
local type, using both the variation in the halo mass function and in the
cluster bias. We find a constraint on the amount of skewness f_NL = 12 +/- 157
(1 sigma) from the cluster data alone.

Validity of Hydrostatic Equilibrium in Galaxy Clusters from Cosmological Hydrodynamical Simulations. (arXiv:1302.5172v1 [astro-ph.CO])

Validity of Hydrostatic Equilibrium in Galaxy Clusters from Cosmological Hydrodynamical Simulations. (arXiv:1302.5172v1 [astro-ph.CO]):
We examine the validity of the hydrostatic equilibrium (HSE) assumption for
galaxy clusters using one of the highest-resolution cosmological hydrodynamical
simulations. We define and evaluate several effective mass terms corresponding
to the Euler equations of the gas dynamics, and quantify the degree of the
validity of HSE in terms of the mass estimate. We find that the mass estimated
under the HSE assumption (the HSE mass) deviates from the true mass by up to ~
30 %. This level of departure from HSE is consistent with the previous claims,
but our physical interpretation is rather different. We demonstrate that the
inertial term in the Euler equations makes a negligible contribution to the
total mass, and the overall gravity of the cluster is balanced by the thermal
gas pressure gradient and the gas acceleration term. Indeed the deviation from
the HSE mass is well explained by the acceleration term at almost all radii. We
also clarify the confusion of previous work due to the inappropriate
application of the Jeans equations in considering the validity of HSE from the
gas dynamics extracted from cosmological hydrodynamical simulations.

Thermodynamics of the Coma Cluster Outskirts. (arXiv:1302.4140v1 [astro-ph.CO])

Thermodynamics of the Coma Cluster Outskirts. (arXiv:1302.4140v1 [astro-ph.CO]):
We present results from a large mosaic of Suzaku observations of the Coma
Cluster, focusing on the thermodynamic properties of the ICM on large scales.
The measured temperature and X-ray brightness profiles are similar along four
relatively undisturbed azimuths probed, with the temperature decreasing from
~8.5 keV at the cluster center to ~2 keV at 2 Mpc. The SW merger boosts the
surface brightness, allowing us to detect X-ray emission out to 2.5 Mpc along
this fifth direction. The X-ray image also reveals two arc-shaped regions with
excess surface brightness towards the east and west of the main cluster core.
These regions appear over-pressured and most likely originate from merger
induced large scale supersonic gas motions. The azimuthally averaged
temperature profile, as well as the deprojected density and pressure profiles
towards the E and NW, all show a sharp drop consistent with an outward
propagating shock front located at the outermost edge of the giant radio halo
observed at 352 MHz with the WSRT and which may be powering this radio
emission. The shape of the entropy profiles along the relatively relaxed E and
NW directions at large radii is consistent with the average profiles of
evolved, well formed cool core clusters, suggesting similar accretion
histories. Our data indicate a flat metal abundance profile at about 0.3 of the
Solar value out to almost the virial radius of Coma, which would favor galactic
winds over ram-pressure stripping as the dominant enrichment mechanism in the
ICM.

X-ray C-M relation: theory and observation. (arXiv:1301.7476v1 [astro-ph.CO])

X-ray C-M relation: theory and observation. (arXiv:1301.7476v1 [astro-ph.CO]):
[Abridged] Since fifteen years, the concentration-mass relation has been
investigated diffusely in theoretical studies. On the other hand, only recently
this relation has been derived from X-ray observations. When that happened, the
results caused a certain level of concern: the X-ray normalizations and slopes
were found significantly dissimilar from those predicted by theory.

By analyzing a total of 52 objects, simulated each time with different
physical recipes for the baryonic component, as well as 60 synthetic X-ray
images, we aim at determining if these discrepancies are real or artificial. In
particular, we investigate how the simulated concentration-mass relation
depends i) on the radial range used to derive the concentration, ii) on the
presence of baryons in the simulations, and on the prescription used to
reproduce the gas. Finally, we evaluate iii) how the results differ when
adopting an X-ray approach for the analysis and iv) how the selection functions
based on X-ray luminosity, temperature, and SZ-signal can impact the results.
All effects studied go in the direction of explaining the discrepancy between
observations and simulations, but they contribute at different levels: while
the fitting radial range and the baryonic component play only a minor role, the
X-ray approach and selection function have profound repercussion on the
results.


RKS Note: Important paper comparing simulated clusters with observed ones, especially in regard to extracting cosmological parameters.

Investigating the Potential Dilution of the Metal Content of Hot Gas in Early-Type Galaxies by Accreted Cold Gas. (arXiv:1301.7706v1 [astro-ph.CO])

Investigating the Potential Dilution of the Metal Content of Hot Gas in Early-Type Galaxies by Accreted Cold Gas. (arXiv:1301.7706v1 [astro-ph.CO]):
The measured emission-weighted metal abundance of the hot gas in early-type
galaxies has been known to be lower than theoretical expectations for 20 years.
In addition, both X-ray luminosity and metal abundance vary significantly among
galaxies of similar optical luminosities. This suggests some missing factors in
the galaxy evolution process, especially the metal enrichment process. With
{\it Chandra} and {\it XMM-Newton}, we studied 32 early-type galaxies (kT
$\lesssim$ 1 keV) covering a span of two orders of $L_{X,\rm gas}/L_{K}$ to
investigate these missing factors. Contrary to previous studies that X-ray
faint galaxies show extremely low Fe abundance ($\sim 0.1$ Z${_\odot}$), nearly
all galaxies in our sample show an Fe abundance at least 0.3 Z${_\odot}$,
although the measured Fe abundance difference between X-ray faint and X-ray
bright galaxies remains remarkable. We investigated whether this dichotomy of
hot gas Fe abundances can be related to the dilution of hot gas by mixing with
cold gas. With a subset of 24 galaxies in this sample, we find that there is
virtually no correlation between hot gas Fe abundances and their atomic gas
content, which disproves the scenario that the low metal abundance of X-ray
faint galaxies might be a result of the dilution of the remaining hot gas by
pristine atomic gas. In contrast, we demonstrate a negative correlation between
the measured hot gas Fe abundance and the ratio of molecular gas mass to hot
gas mass, although it is unclear what is responsible for this apparent
anti-correlation. We discuss several possibilities including that externally
originated molecular gas might be able to dilute the hot gas metal content.

Dark Matter Subhalos and the X-ray Morphology of the Coma Cluster. (arXiv:1302.1917v1 [astro-ph.CO])

Dark Matter Subhalos and the X-ray Morphology of the Coma Cluster. (arXiv:1302.1917v1 [astro-ph.CO]):
Structure formation models predict that clusters of galaxies contain numerous
massive subhalos. The gravity of a subhalo in a cluster compresses the
surrounding intracluster gas and enhances its X-ray emission. We present a
simple model, which treats subhalos as slow moving and gasless, for computing
this effect. Recent weak lensing measurements by Okabe et al. (2010) have
determined masses of ~ 10^13 solar masses for three mass concentrations
projected within 300 kpc of the center of the Coma cluster, two of which are
centered on the giant elliptical galaxies NGC 4889 and NGC 4874. Adopting a
smooth spheroidal beta-model for the gas distribution in the unperturbed
cluster, we model the effect of these subhalos on the X-ray morphology of the
Coma cluster, comparing our results to Chandra and XMM-Newton X-ray data. The
agreement between the models and the X-ray morphology of the central Coma
cluster is striking. With subhalo parameters from the lensing measurements, the
distances of the three subhalos from the Coma cluster midplane along our line
of sight are all tightly constrained. Using the model to fit the subhalo masses
for NGC 4889 and NGC 4874 gives 9.1 x 10^12 and 7.6 x 10^12 solar masses,
respectively, in good agreement with the lensing masses. These results lend
strong support to the argument that NGC 4889 and NGC 4874 are each associated
with a subhalo that resides near the center of the Coma cluster. In addition to
constraining the masses and 3-d location of subhalos, the X-ray data show
promise as a means of probing the structure of central subhalos.

Suzaku observations of Abell 1835 outskirts: Deviation from hydrostatic equilibrium. (arXiv:1302.0095v1 [astro-ph.CO])

Suzaku observations of Abell 1835 outskirts: Deviation from hydrostatic equilibrium. (arXiv:1302.0095v1 [astro-ph.CO]):
We present results of four-pointing Suzaku X-ray observations (total ~200 ks)
of the intracluster medium (ICM) in the Abell 1835 galaxy cluster (kT ~ 8 keV,
z = 0.253) out to the virial radius (r_vir ~ 2.9 Mpc) and beyond. Faint X-ray
emission from the ICM out to r_vir is detected. The temperature gradually
decreases with radius from ~8 keV in the inner region to ~2 keV at r_vir. The
entropy profile is shown to flatten beyond r_500, in disagreement with the
r_1.1 dependence predicted from the accretion shock heating model. The thermal
pressure profile in the range 0.3r_500 < r < r_vir agrees well with that
obtained from the stacked Sunyaev-Zel'dovich effect observations with the
Planck satellite. The hydrostatic mass profile in the cluster outskirts (r_500
< r < r_vir) falls well short of the weak lensing one derived from
Subaru/Suprime-Cam observations, showing an unphysical decrease with radius.
The gas mass fraction at r_vir defined with the lensing total mass agrees with
the cosmic baryon fraction from the WMAP 7-year data. All these results
indicate, rather than the gas-clumping effect, that the bulk of the ICM in the
cluster outskirts is far from hydrostatic equilibrium and infalling matter
retained some of its kinetic energy. Finally, combining with our recent Suzaku
and lensing analysis of Abell 1689, a cluster of similar mass, temperature, and
redshift, we show that the cluster temperature distribution in the outskirts is
significantly correlated with the galaxy density field in the surrounding
large-scale environment at (1-2)r_vir.

Relative velocity of dark matter and barions in clusters of galaxies and measurements of their peculiar velocities. (arXiv:1301.0024v1 [astro-ph.CO])

Relative velocity of dark matter and barions in clusters of galaxies and measurements of their peculiar velocities. (arXiv:1301.0024v1 [astro-ph.CO]):
The increasing sensitivity of current experiments, which nowadays routinely
measure the thermal SZ effect within galaxy clusters, provide the hope that
peculiar velocities of individual clusters of galaxies will be measured rather
soon using the kinematic SZ effect. Also next generation of X-ray telescopes
with microcalorimeters, promise first detections of the motion of the intra
cluster medium (ICM) within clusters. We used a large set of cosmological,
hydrodynamical simulations, which cover very large cosmological volume, hosting
a large number of rich clusters of galaxies, as well as moderate volumes where
the internal structures of individual galaxy clusters can be resolved with very
high resolution to investigate, how the presence of baryons and their
associated physical processes like cooling and star-formation are affecting the
systematic difference between mass averaged velocities of dark matter and the
ICM inside a cluster. We, for the first time, quantify the peculiar motion of
galaxy clusters as function of the large scale environment. We also demonstrate
that especially in very massive systems, the relative velocity of the ICM
compared to the cluster peculiar velocity add significant scatter onto the
inferred peculiar velocity, especially when measurements are limited to the
central regions of the cluster. Depending on the aperture used, this scatter
varies between 50% and 20%, when going from the core (e.g. ten percent of the
virial radius) to the full cluster (e.g. the virial radius).

The Atacama Cosmology Telescope: Sunyaev-Zel'dovich Selected Galaxy Clusters at 148 GHz from Three Seasons of Data. (arXiv:1301.0816v1 [astro-ph.CO])

The Atacama Cosmology Telescope: Sunyaev-Zel'dovich Selected Galaxy Clusters at 148 GHz from Three Seasons of Data. (arXiv:1301.0816v1 [astro-ph.CO]):
[Abridged] We present a catalog of 68 galaxy clusters, of which 19 are new
discoveries, detected via the Sunyaev-Zel'dovich effect (SZ) at 148 GHz in the
Atacama Cosmology Telescope (ACT) survey of 504 square degrees on the celestial
equator. A subsample of 48 clusters within the 270 square degree region
overlapping SDSS Stripe 82 is estimated to be 90% complete for M_500c > 4.5e14
Msun and 0.15 < z < 0.8. While matched filters are used to detect the clusters,
the sample is studied further through a "Profile Based Amplitude Analysis"
using a single filter at a fixed \theta_500 = 5.9' angular scale. This new
approach takes advantage of the "Universal Pressure Profile" (UPP) to break the
degeneracy between the cluster extent (R_500) and the integrated Compton
parameter (Y_500). The UPP scalings are found to be nearly identical to an
adiabatic model, while a model incorporating non-thermal pressure better
matches dynamical mass measurements and masses from the South Pole Telescope. A
complete, high signal to noise ratio subsample of 15 ACT clusters is used to
obtain cosmological constraints. We first confirm that constraints from SZ data
are limited by uncertainty in the scaling relation parameters rather than
sample size or measurement uncertainty. We next add in seven clusters from the
ACT Southern survey, including their dynamical mass measurements based on
galaxy velocity dispersions. In combination with WMAP7 these data
simultaneously constrain the scaling relation and cosmological parameters,
yielding \sigma_8 = 0.829 \pm 0.024 and \Omega_m = 0.292 \pm 0.025. The results
include marginalization over a 15% bias in dynamical mass relative to the true
halo mass. In an extension to LCDM that incorporates non-zero neutrino mass
density, we combine our data with WMAP7+BAO+Hubble constant measurements to
constrain \Sigma m_\nu < 0.29 eV (95% C. L.).

Metal-mass-to-light ratios of the Perseus cluster out to the virial radius. (arXiv:1301.0655v1 [astro-ph.CO])

Metal-mass-to-light ratios of the Perseus cluster out to the virial radius. (arXiv:1301.0655v1 [astro-ph.CO]):
We analyzed XMM-Newton data of the Perseus cluster out to $\sim$1 Mpc, or
approximately half the virial radius. Using the flux ratios of Lyalpha lines of
H-like Si and S to Kalpha line of He-like Fe, the abundance ratios of Si/Fe and
S/Fe of the intracluster medium (ICM) were derived using the APEC plasma code
v2.0.1. The temperature dependence of the line ratio limits the systematic
uncertainty in the derived abundance ratio. The Si/Fe and S/Fe in the ICM of
the Perseus cluster show no radial gradient. The emission-weighted averages of
the Si/Fe and S/Fe ratios outside the cool core are 0.91 +- 0.08 and 0.93 +-
0.10, respectively, in solar units according to the solar abundance table of
Lodders (2003). These ratios indicate that most Fe was synthesized by
supernovae Ia. We collected K-band luminosities of galaxies and calculated the
ratio of Fe and Si mass in the ICM to K-band luminosity, iron-mass-to-light
ratio (IMLR) and silicon-mass-to-light ratio (SMLR). Within $\sim$1 Mpc, the
cumulative IMLR and SMLR increase with radius. Using Suzaku data for the
northwest and east directions, we also calculated the IMLR out to $\sim$ 1.8
Mpc, or about the virial radius. We constrained the SMLR out to this radius and
discussed the slope of the initial mass function of stars in the cluster. Using
the cumulative IMLR profile, we discuss the past supernova Ia rate.

The X-ray/SZ view of the virial region. II. Gas mass fraction. (arXiv:1301.0624v1 [astro-ph.CO])

The X-ray/SZ view of the virial region. II. Gas mass fraction. (arXiv:1301.0624v1 [astro-ph.CO]):
Several recent studies used the hot gas fraction of galaxy clusters as a
standard ruler to constrain dark energy, which provides competitive results
compared to other techniques. This method, however, relies on the assumption
that the baryon fraction in clusters agrees with the cosmic value
Omega_b/Omega_m, and does not differ from one system to another. We test this
hypothesis by measuring the gas mass fraction over the entire cluster volume in
a sample of local clusters. Combining the SZ thermal pressure from Planck and
the X-ray gas density from ROSAT, we measured for the first time the average
gas fraction (fgas) out to the virial radius and beyond in a large sample of
clusters. We also obtained azimuthally-averaged measurements of the gas
fraction for 18 individual systems, which we used to compute the scatter of
fgas around the mean value at different radii and its dependence on the
cluster's temperature. The gas mass fraction increases with radius and reaches
the cosmic baryon fraction close to R200. At R200, we measure
fgas,200=0.176+/-0.009. We find significant differences between the baryon
fraction of relaxed, cool-core (CC) systems and unrelaxed, non-cool core (NCC)
clusters in the outer regions. In average, the gas fraction in NCC clusters
slightly exceeds the cosmic baryon fraction, while in CC systems the gas
fraction converges to the expected value when accounting for the stellar
content, without any evidence for variations from one system to another. We
find that fgas estimates in NCC systems slightly disagree with the cosmic value
approaching R200. This result could be explained either by a violation of the
assumption of hydrostatic equilibrium or by an inhomogeneous distribution of
the gas mass. Conversely, cool-core clusters are found to provide reliable
constraints on fgas at overdensities >200, which makes them suitable for
cosmological studies.

The X-ray/SZ view of the virial region. I. Thermodynamic properties. (arXiv:1301.0617v1 [astro-ph.CO])

The X-ray/SZ view of the virial region. I. Thermodynamic properties. (arXiv:1301.0617v1 [astro-ph.CO]):
We measure the thermodynamic properties of cluster outer regions to provide
constraints on the processes that rule the formation of large scale structures.
We derived the thermodynamic properties of the intracluster gas (temperature,
entropy) by combining the SZ thermal pressure from Planck and the X-ray gas
density from ROSAT. This method allowed us to reconstruct for the first time
temperature and entropy profiles out to the virial radius and beyond in a large
sample of objects. At variance with several recent Suzaku studies, we find that
the entropy rises steadily with radius, albeit at at a somewhat lower rate than
predicted by self-similar expectations. We note significant differences between
relaxed, cool-core systems and unrelaxed clusters in the outer regions. Relaxed
systems appear to follow the self-similar expectations more closely than
perturbed objects. Our results indicate that the well-known entropy excess
observed in cluster cores extends well beyond the central regions. When
correcting for the gas depletion, the observed entropy profiles agree with the
prediction from gravitational collapse only, especially for cool-core clusters.

Investigation of X-ray cavities in the cooling flow system Abell 1991. (arXiv:1301.2928v1 [astro-ph.CO])

Investigation of X-ray cavities in the cooling flow system Abell 1991. (arXiv:1301.2928v1 [astro-ph.CO]):
We present results based on the systematic analysis of \textit{Chandra}
archive data on the X-ray bright Abell Richness class-I type cluster Abell 1991
with an objective to investigate properties of the X-ray cavities hosted by
this system. The unsharp masked image as well as 2-d $\beta$ model subtracted
residual image of Abell 1991 reveals a pair of X-ray cavities and a region of
excess emission in the central $\sim$12 kpc region. Both the cavities are of
ellipsoidal shape and exhibit an order of magnitude deficiency in the X-ray
surface brightness compared to that in the undisturbed regions. Spectral
analysis of X-ray photons extracted from the cavities lead to the temperature
values equal to $1.77_{-0.12}^{+0.19}$ keV for N-cavity and
$1.53_{-0.06}^{+0.05}$ keV for S-cavity, while that for the excess X-ray
emission region is found to be equal to $2.06_{-0.07}^{+0.12}$ keV. Radial
temperature profile derived for Abell 1991 reveals a positive temperature
gradient, reaching to a maximum of 2.63 keV at $\sim$ 76 kpc and then declines
in outward direction. 0.5$-$2.0 keV soft band image of the central 15\arcsec
region of Abell 1991 reveals relatively cooler three different knot like
features that are about 10\arcsec off the X-ray peak of the cluster. Total
power of the cavities is found to be equal to $\sim 8.64\times 10^{43}$ \lum,
while the X-ray luminosity within the cooling radius is found to be 6.04
$\times 10^{43}$ \lum, comparison of which imply that the mechanical energy
released by the central AGN outburst is sufficient to balance the radiative
loss.

A scientific case for future X-ray Astronomy: Galaxy Clusters at high redshifts. (arXiv:1301.5202v1 [astro-ph.CO])

A scientific case for future X-ray Astronomy: Galaxy Clusters at high redshifts. (arXiv:1301.5202v1 [astro-ph.CO]):
Clusters of galaxies at high redshift (z>1) are vitally important to
understand the evolution of the large scale structure of the Universe, the
processes shaping galaxy populations and the cycle of the cosmic baryons, and
to constrain cosmological parameters. After 13 years of operation of the
Chandra and XMM-Newton satellites, the discovery and characterization of
distant X-ray clusters is proceeding at a slow pace, due to the low solid angle
covered so far, and the time-expensive observations needed to physically
characterize their intracluster medium (ICM). At present, we know that at z>1
many massive clusters are fully virialized, their ICM is already enriched with
metals, strong cool cores are already in place, and significant star formation
is ongoing in their most massive galaxies, at least at z>1.4. Clearly, the
assembly of a large and well characterized sample of high-z X-ray clusters is a
major goal for the future. We argue that the only means to achieve this is a
survey-optimized X-ray mission capable of offering large solid angle, high
sensitivity, good spectral coverage, low background and angular resolution as
good as 5 arcsec.

Perspectives on Intracluster Enrichment and the Stellar Initial Mass Function in Elliptical Galaxies. (arXiv:1301.3200v1 [astro-ph.CO])

Perspectives on Intracluster Enrichment and the Stellar Initial Mass Function in Elliptical Galaxies. (arXiv:1301.3200v1 [astro-ph.CO]):
The amount of metals in the Intracluster Medium (ICM) in rich galaxy clusters
exceeds that expected based on the observed stellar population by a large
factor. We quantify this discrepancy -- which we term the "cluster elemental
abundance paradox" -- and investigate the required properties of the
ICM-enriching population. The necessary enhancement in metal enrichment may, in
principle, originate in the observed stellar population if a larger fraction of
stars in the supernova-progenitor mass range form from an initial mass function
(IMF) that is either bottom-light or top-heavy, with the latter in some
conflict with observed ICM abundance ratios. Other alternatives that imply more
modest revisions to the IMF, mass return and remnant fractions, and primordial
fraction, posit an increase in the fraction of 3-8 solar mass stars that
explode as SNIa or assume that there are more stars than conventionally thought
-- although the latter implies a high star formation efficiency. We discuss the
feasibility of these various solutions and the implications for the diversity
of star formation, the process of elliptical galaxy formation, and the nature
of this "hidden" source of ICM metal enrichment in light of recent evidence of
an elliptical galaxy IMF that, because it is skewed to low masses, deepens the
paradox.

Distant galaxy clusters in a deep XMM-Newton field within the CFTHLS D4. (arXiv:1301.3506v1 [astro-ph.CO])

Distant galaxy clusters in a deep XMM-Newton field within the CFTHLS D4. (arXiv:1301.3506v1 [astro-ph.CO]):
The XMM-Newton Distant Cluster Project (XDCP) aims at the identification of a
well defined sample of X-ray selected clusters of galaxies at redshifts z>0.8.
We present a catalogue of the extended sources in one the deepest ~250 ksec
XMM-Newton fields targeting LBQS 2215-175 covering the CFHTLS deep field four.
The cluster identification is based, among others, on deep imaging with the ESO
VLT and from the CFHT legacy survey. The confirmation of cluster candidates is
done by VLT/FORS2 multi-object spectroscopy. Photometric redshifts from the
CFHTLS D4 are utilized to confirm the effectiveness of the X-ray cluster
selection method. The survey sensitivity is computed with extensive
simulations. At a flux limit of S(0.5-2.0 keV) ~ 2.5e-15 erg/s we achieve a
completeness level higher than 50% in an area of ~0.13 square degrees. We
detect six galaxy clusters above this limit with optical counterparts, of which
5 are new spectroscopic discoveries. Two newly discovered X-ray luminous galaxy
clusters are at z>1.0, another two at z=0.41 and one at z=0.34. For the most
distant X-ray selected cluster in this field at z=1.45 we find additional
(active) member galaxies from both X-ray and spectroscopic data. Additionally,
we find evidence of large scale structures at moderate redshifts of z=0.41 and
z=0.34. The quest for distant clusters in archival XMM-Newton data has led to
the detection of six clusters in a single field, making XMM-Newton an
outstanding tool for cluster surveys. Three of these clusters are at z>1, which
emphasises the valuable contribution of small, yet deep surveys to cosmology.
Beta-models are appropriate descriptions for the cluster surface brightness to
perform cluster detection simulations in order to compute the X-ray selection
function. The constructed logN-logS tends to favour a scenario where no
evolution in the cluster X-ray luminosity function (XLF) takes place.

Updated catalog of 132,684 galaxy clusters and evolution of brightest cluster galaxies. (arXiv:1301.0871v1 [astro-ph.CO])

Updated catalog of 132,684 galaxy clusters and evolution of brightest cluster galaxies. (arXiv:1301.0871v1 [astro-ph.CO]):
We identified 132,684 clusters in the redshift range of 0.05<z<0.8 from SDSS
DR8. The spectroscopic redshifts of 52,683 clusters have been included in the
catalog using SDSS DR9 data. We found that BCGs are more luminous in richer
clusters and at higher redshifts.

Bulk motion measurements in clusters of galaxies with ATHENA-like missions. (arXiv:1301.1852v1 [astro-ph.CO])

Bulk motion measurements in clusters of galaxies with ATHENA-like missions. (arXiv:1301.1852v1 [astro-ph.CO]):
The hierarchical formation of clusters of galaxies by accretion of material
releases gravitational energy which dissipates into the intracluster gas. The
process heats the material and generates gas turbulence and bulk motions and
thus kinetic pressure. Mapping the velocity fields of the moving subunits would
enable a new diagnostics tool for cluster formation studies and unbiased X-ray
mass estimates. The required spatially resolved high resolution spectroscopy is
not currently available. I demonstrate here the feasibility of detecting and
mapping the velocities of the bulk motions using the Doppler shift of the Fe
XXV K alpha line with the proposed ATHENA satellite.

Planck Intermediate Results. XI: The gas content of dark matter halos: the Sunyaev-Zeldovich-stellar mass relation for locally brightest galaxies. (arXiv:1212.4131v1 [astro-ph.CO])

Planck Intermediate Results. XI: The gas content of dark matter halos: the Sunyaev-Zeldovich-stellar mass relation for locally brightest galaxies. (arXiv:1212.4131v1 [astro-ph.CO]):
We present the scaling relation between Sunyaev-Zeldovich (SZ) signal and
stellar mass for almost 260,000 locally brightest galaxies (LBGs) selected from
the Sloan Digital Sky Survey (SDSS). These are predominantly the central
galaxies of their dark matter halos. We calibrate the stellar-to-halo mass
conversion using realistic mock catalogues based on the Millennium Simulation.
Applying a multi-frequency matched filter to the Planck data for each LBG, and
averaging the results in bins of stellar mass, we measure the mean SZ signal
down to $M_\ast\sim 2\times 10^{11} \Msolar$, with a clear indication of signal
at even lower stellar mass. We derive the scaling relation between SZ signal
and halo mass by assigning halo properties from our mock catalogues to the real
LBGs and simulating the Planck observation process. This relation shows no
evidence for deviation from a power law over a halo mass range extending from
rich clusters down to $M_{500}\sim 2\times 10^{13} \Msolar$, and there is a
clear indication of signal down to $M_{500}\sim 4\times 10^{12} \Msolar$.
Planck's SZ detections in such low-mass halos imply that about a quarter of all
baryons have now been seen in the form of hot halo gas, and that this gas must
be less concentrated than the dark matter in such halos in order to remain
consistent with X-ray observations. At the high-mass end, the measured SZ
signal is 20% lower than found from observations of X-ray clusters, a
difference consistent with Malmquist bias effects in the X-ray sample.

The X-ray-Optical Relations for Nine Clusters at z = 0.7-1.1. (arXiv:1212.4219v1 [astro-ph.CO])

The X-ray-Optical Relations for Nine Clusters at z = 0.7-1.1. (arXiv:1212.4219v1 [astro-ph.CO]):
We use Chandra observations of nine optically and X-ray selected clusters in
five different structures at z ~ 0.7-1.1 from the Observations of Redshift
Evolution in Large-Scale Environments (ORELSE) survey to study diffuse X-ray
emission from galaxy clusters. X-ray gas temperatures and bolometric rest-frame
luminosities are measured for each cluster in the sample. We present new
redshift measurements, derived from dataobtained using the Deep Imaging
Multi-Object Spectrograph on the Keck 10-m telescope, for two clusters in the
RX J0910 supercluster at z ~ 1.1, from which velocity dispersions are measured.
Dispersions for all clusters are combined with X-ray luminosities and gas
temperatures to evaluate how the cluster properties compare to low-redshift
scaling relations. We also measure the degree of substructure in each cluster
by examining the velocity histograms, performing Dressler-Shectman tests, and
computing the offsets between the X-ray emission center and optically-derived
centroids. We find that only two clusters show clear indications of being
unrelaxed, based on their scaling relations and other dynamical state
diagnostics. Using our sample, we evaluate the redshift evolution of the L_x-T
relation and investigate the implications of our results for precision
cosmology surveys.