Distant galaxy clusters in the XMM Large Scale Structure survey. (arXiv:1212.4185v1 [astro-ph.CO])

Distant galaxy clusters in the XMM Large Scale Structure survey. (arXiv:1212.4185v1 [astro-ph.CO]):
(Abridged) Distant galaxy clusters provide important tests of the growth of
large scale structure in addition to highlighting the process of galaxy
evolution in a consistently defined environment at large look back time. We
present a sample of 22 distant (z>0.8) galaxy clusters and cluster candidates
selected from the 9 deg2 footprint of the overlapping X-ray Multi Mirror (XMM)
Large Scale Structure (LSS), CFHTLS Wide and Spitzer SWIRE surveys. Clusters
are selected as extended X-ray sources with an accompanying overdensity of
galaxies displaying optical to mid-infrared photometry consistent with z>0.8.
Nine clusters have confirmed spectroscopic redshifts in the interval 0.8<z<1.2,
four of which are presented here for the first time. A further 11 candidate
clusters have between 8 and 10 band photometric redshifts in the interval
0.8<z<2.2, while the remaining two candidates do not have information in
sufficient wavebands to generate a reliable photometric redshift. All of the
candidate clusters reported in this paper are presented for the first time.
Those confirmed and candidate clusters with available near infrared photometry
display evidence for a red sequence galaxy population, determined either
individually or via a stacking analysis, whose colour is consistent with the
expectation of an old, coeval stellar population observed at the cluster
redshift. We further note that the sample displays a large range of red
fraction values indicating that the clusters may be at different stages of red
sequence assembly. We compare the observed X-ray emission to the flux expected
from a suite of model clusters and find that the sample displays an effective
mass limit M200 ~ 1e14 Msolar with all clusters displaying masses consistent
with M200 < 5e14 Msolar. This XMM distant cluster study represents a complete
sample of X-ray selected z>0.8 clusters.

Dark matter and cosmic structure. (arXiv:1210.0544v1 [astro-ph.CO])

Dark matter and cosmic structure. (arXiv:1210.0544v1 [astro-ph.CO]):
We review the current standard model for the evolution of cosmic structure,
tracing its development over the last forty years and focusing specifically on
the role played by numerical simulations and on aspects related to the nature
of dark matter.

X-ray Bright Active Galactic Nuclei in Massive Galaxy Clusters I: Number Counts and Spatial Distribution. (arXiv:1209.2132v1 [astro-ph.CO])

X-ray Bright Active Galactic Nuclei in Massive Galaxy Clusters I: Number Counts and Spatial Distribution. (arXiv:1209.2132v1 [astro-ph.CO]):
We present an analysis of the X-ray bright point source population in 43
massive clusters of galaxies observed with the Chandra X-ray Observatory. We
have constructed a catalog of 4210 rigorously selected X-ray point sources in
these fields, which span a survey area of 4.2 square degrees. This catalog
reveals a clear excess of sources when compared to deep blank-field surveys,
which amounts to roughly 1 additional source per cluster, likely Active
Galactic Nuclei (AGN) associated with the clusters. The excess sources are
concentrated within the virial radii of the clusters, with the largest excess
observed near the cluster centers. The average radial profile of the excess
X-ray sources of the cluster are well described by a power law (N(r) ~ r^\beta)
with an index of \beta ~ -0.5. An initial analysis using literature results on
the mean profile of member galaxies in massive X-ray selected clusters
indicates that the fraction of galaxies hosting X-ray AGN rises with increasing
clustercentric radius, being approximately 5 to 10 times higher near the virial
radius than in the central regions. This trend is qualitatively similar to that
observed for star formation in cluster member galaxies.

The dark matter distribution in z~0.5 clusters of galaxies. I : Determining scaling relations with weak lensing masses. (arXiv:1208.4026v1 [astro-ph.CO])

The dark matter distribution in z~0.5 clusters of galaxies. I : Determining scaling relations with weak lensing masses. (arXiv:1208.4026v1 [astro-ph.CO]):
The total mass of clusters of galaxies is a key parameter to study massive
halos. It relates to numerous gravitational and baryonic processes at play in
the framework of large scale structure formation, thus rendering its
determination important but challenging. From a sample of the 11 X-ray bright
clusters selected from the excpres sample, we investigate the optical and X-ray
properties of clusters with respect to their total mass derived from weak
gravitational lensing. From multi-color wide field imaging obtained with
MegaCam at CFHT, we derive the shear profile of each individual cluster of
galaxies. We perform a careful investigation of all systematic sources related
to the weak lensing mass determination. The weak lensing masses are then
compared to the X-ray masses obtained from the analysis of XMM observations and
assuming hydrostatic equilibrium. We find a good agreement between the two mass
proxies although a few outliers with either perturbed morphology or poor
quality data prevent to derive robust mass estimates. The weak lensing mass is
also correlated with the optical richness and the total optical luminosity, as
well as with the X-ray luminosity, to provide scaling relations within the
redshift range 0.4<z<0.6. These relations are in good agreement with previous
works at lower redshifts. For the L_X-M relation we combine our sample with two
other cluster and group samples from the literature, thus covering two decades
in mass and X-ray luminosity, with a regular and coherent correlation between
the two physical quantities.

Toward an accurate mass function for precision cosmology. (arXiv:1206.5302v1 [astro-ph.CO])

Toward an accurate mass function for precision cosmology. (arXiv:1206.5302v1 [astro-ph.CO]):
Cosmological surveys aim to use the evolution of the abundance of galaxy
clusters to accurately constrain the cosmological model. In the context of
LCDM, we show that it is possible to achieve the required percent level
accuracy in the halo mass function with gravity-only cosmological simulations,
and we provide simulation start and run parameter guidelines for doing so. Some
previous works have had sufficient statistical precision, but lacked robust
verification of absolute accuracy. Convergence tests of the mass function with,
for example, simulation start redshift can exhibit false convergence of the
mass function due to counteracting errors, potentially misleading one to infer
overly optimistic estimations of simulation accuracy. Percent level accuracy is
possible if initial condition particle mapping uses second order Lagrangian
Perturbation Theory, and if the start epoch is between 10 and 50 expansion
factors before the epoch of halo formation of interest. The mass function for
halos with fewer than ~1000 particles is highly sensitive to simulation
parameters and start redshift, implying a practical minimum mass resolution
limit due to mass discreteness. The narrow range in converged start redshift
suggests that it is not presently possible for a single simulation to capture
accurately the cluster mass function while also starting early enough to model
accurately the numbers of reionisation era galaxies, whose baryon feedback
processes may affect later cluster properties. Ultimately, to fully exploit
current and future cosmological surveys will require accurate modeling of
baryon physics and observable properties, a formidable challenge for which
accurate gravity-only simulations are just an initial step.

Discovery of radio halos and double-relics in distant MACS galaxy clusters: clues to the efficiency of particle acceleration. (arXiv:1206.6102v1 [astro-ph.CO])

Discovery of radio halos and double-relics in distant MACS galaxy clusters: clues to the efficiency of particle acceleration. (arXiv:1206.6102v1 [astro-ph.CO]):
We have performed 323 MHz observations with the Giant Metrewave Radio
Telescope of the most promising candidates selected from the MACS catalog. The
aim of the work is to extend our knowledge of the radio halo and relic
populations to z>0.3, the epoch in which massive clusters formed. In
MACSJ1149.5+2223 and MACSJ1752.1+4440, we discovered two double-relic systems
with a radio halo, and in MACSJ0553.4-3342 we found a radio halo. Archival Very
Large Array observations and Westerbork Synthesis Radio Telescope observations
have been used to study the polarization and spectral index properties. The
radio halo in MACSJ1149.5+2223 has the steepest spectrum ever found so far in
these objects (alpha > 2). The double relics in MACSJ1149.5+2223 are peculiar
in their position that is misaligned with the main merger axis. The relics are
polarized up to 30% and 40% in MACSJ1149.5+2223 and MACSJ1752.040+44,
respectively. In both cases, the magnetic field is roughly aligned with the
relics' main axes. The spectra in the relics in MACSJ1752.040+44 steepen
towards the cluster centre, in agreement with model expectations. X-ray data on
MACSJ0553.4-3342 suggests that this cluster is undergoing a major merger, with
the merger axis close to the plane of the sky. The cores of the disrupted
clusters have just passed each other, but no radio relic is detected in this
system. If turbulence is responsible for the radio emission, we argue that it
must develop before the core passage. A comparison of double relic plus halo
system with cosmological simulations allows a simultaneous estimate of the
acceleration efficiencies at shocks (to produce relics) and of turbulence (to
produce the halo).

The Chandra X-ray point source catalog in the DEEP2 Galaxy Redshift Survey fields. (arXiv:1206.6884v1 [astro-ph.HE])

The Chandra X-ray point source catalog in the DEEP2 Galaxy Redshift Survey fields. (arXiv:1206.6884v1 [astro-ph.HE]):
We present the X-ray point-source catalog produced from the Chandra Advanced
CCD Imaging Spectrometer (ACIS-I) observations of the combined \sim3.2 deg2
DEEP2 (XDEEP2) survey fields, which consist of four ~0.7-1.1 deg2 fields. The
combined total exposures across all four XDEEP2 fields range from ~10ks-1.1Ms.
We detect X-ray point-sources in both the individual ACIS-I observations and
the overlapping regions in the merged (stacked) images. We find a total of 2976
unique X-ray sources within the survey area with an expected false-source
contamination of ~30 sources (~1%). We present the combined logN-logS
distribution of sources detected across the XDEEP2 survey fields and find good
agreement with the Extended Chandra Deep Field and Chandra-COSMOS fields to
f_{X,0.5-2keV}\sim2x10^{-16} erg/cm^2/s. Given the large survey area of XDEEP2,
we additionally place relatively strong constraints on the logN-logS
distribution at high fluxes (f_{X,0.5-2keV}\sim3x10^{-14} erg/cm^2/s), and find
a small systematic offset (a factor ~1.5) towards lower source numbers in this
regime, when compared to smaller area surveys. The number counts observed in
XDEEP2 are in close agreement with those predicted by X-ray background
synthesis models. Additionally, we present a Bayesian-style method for
associating the X-ray sources with optical photometric counterparts in the
DEEP2 catalog (complete to R_AB < 25.2) and find that 2126 (~71.4\pm2.8%) of
the 2976 X-ray sources presented here have a secure optical counterpart with a
<6% contamination fraction. We provide the DEEP2 optical source properties
(e.g., magnitude, redshift) as part of the X-ray-optical counterpart catalog.

Cosmological Constraints from a Combination of Galaxy Clustering & Lensing -- II. Fisher Matrix Analysis. (arXiv:1207.0004v1 [astro-ph.CO])

Cosmological Constraints from a Combination of Galaxy Clustering & Lensing -- II. Fisher Matrix Analysis. (arXiv:1207.0004v1 [astro-ph.CO]):
We quantify the accuracy with which the cosmological parameters
characterizing the energy density of matter (\Omega_m), the amplitude of the
power spectrum of matter fluctuations (\sigma_8), the energy density of
neutrinos (\Omega_{\nu}) and the dark energy equation of state (w_0) can be
constrained using data from large galaxy redshift surveys. We advocate a joint
analysis of the abundance of galaxies, galaxy clustering, and the galaxy-galaxy
weak lensing signal in order to simultaneously constrain the halo occupation
statistics (i.e., galaxy bias) and the cosmological parameters of interest. We
parameterize the halo occupation distribution of galaxies in terms of the
conditional luminosity function and use the analytical framework of the halo
model described in our companion paper (van den Bosch et al. 2012), to predict
the relevant observables. By performing a Fisher matrix analysis, we show that
a joint analysis of these observables, even with the precision with which they
are currently measured from the Sloan Digital Sky Survey, can be used to obtain
tight constraints on the cosmological parameters, fully marginalized over
uncertainties in galaxy bias. We demonstrate that the cosmological constraints
from such an analysis are nearly uncorrelated with the halo occupation
distribution constraints, thus, minimizing the systematic impact of any
imperfections in modeling the halo occupation statistics on the cosmological
constraints. In fact, we demonstrate that the constraints from such an analysis
are both complementary to and competitive with existing constraints on these
parameters from a number of other techniques, such as cluster abundances,
cosmic shear and/or baryon acoustic oscillations, thus paving the way to test
the concordance cosmological model.

Cosmological Constraints from a Combination of Galaxy Clustering and Lensing -- III. Application to SDSS Data. (arXiv:1207.0503v1 [astro-ph.CO])

Cosmological Constraints from a Combination of Galaxy Clustering and Lensing -- III. Application to SDSS Data. (arXiv:1207.0503v1 [astro-ph.CO]):
We simultaneously constrain cosmology and galaxy bias using measurements of
galaxy abundances, galaxy clustering and galaxy-galaxy lensing taken from the
Sloan Digital Sky Survey. We use the conditional luminosity function (which
describes the halo occupation statistics as function of galaxy luminosity)
combined with the halo model (which describes the non-linear matter field in
terms of its halo building blocks) to describe the galaxy-dark matter
connection. We explicitly account for residual redshift space distortions in
the projected galaxy-galaxy correlation functions, and marginalize over
uncertainties in the scale dependence of the halo bias and the detailed
structure of dark matter haloes. Under the assumption of a spatially flat,
vanilla {\Lambda}CDM cosmology, we focus on constraining the matter density,
{\Omega}m, and the normalization of the matter power spectrum, {\sigma}8, and
we adopt WMAP7 priors for the spectral index, the Hubble parameter, and the
baryon density. We obtain that \Omegam = 0.278_{-0.026}^{+0.023} and {\sigma}8
= 0.763_{-0.049}^{+0.064} (95% CL). These results are robust to uncertainties
in the radial number density distribution of satellite galaxies, while allowing
for non-Poisson satellite occupation distributions results in a slightly lower
value for {\sigma}8 (0.744_{-0.047}^{+0.056}). These constraints are in
excellent agreement (at the 1{\sigma} level) with the cosmic microwave
background constraints from WMAP. This demonstrates that the use of a realistic
and accurate model for galaxy bias, down to the smallest non-linear scales
currently observed in galaxy surveys, leads to results perfectly consistent
with the vanilla {\Lambda}CDM cosmology.

A filament of dark matter between two clusters of galaxies. (arXiv:1207.0809v1 [astro-ph.CO])

A filament of dark matter between two clusters of galaxies. (arXiv:1207.0809v1 [astro-ph.CO]):
It is a firm prediction of the concordance Cold Dark Matter (CDM)
cosmological model that galaxy clusters live at the intersection of large-scale
structure filaments. The thread-like structure of this "cosmic web" has been
traced by galaxy redshift surveys for decades. More recently the Warm-Hot
Intergalactic Medium (WHIM) residing in low redshift filaments has been
observed in emission and absorption. However, a reliable direct detection of
the underlying Dark Matter skeleton, which should contain more than half of all
matter, remained elusive, as earlier candidates for such detections were either
falsified or suffered from low signal-to-noise ratios and unphysical
misalignements of dark and luminous matter. Here we report the detection of a
dark matter filament connecting the two main components of the Abell 222/223
supercluster system from its weak gravitational lensing signal, both in a
non-parametric mass reconstruction and in parametric model fits. This filament
is coincident with an overdensity of galaxies and diffuse, soft X-ray emission
and contributes mass comparable to that of an additional galaxy cluster to the
total mass of the supercluster. Combined with X-ray observations, we place an
upper limit of 0.09 on the hot gas fraction, the mass of X-ray emitting gas
divided by the total mass, in the filament.

Tidal interaction vs. ram pressure stripping effects as seen in X-rays. Hot gas in group and cluster galaxies. (arXiv:1207.1684v1 [astro-ph.CO])

Tidal interaction vs. ram pressure stripping effects as seen in X-rays. Hot gas in group and cluster galaxies. (arXiv:1207.1684v1 [astro-ph.CO]):
The hot intracluster/intragroup medium (ICM/IGM) and a high galaxy density
can lead to perturbations of the galactic interstellar medium (ISM) due to ram
pressure and/or tidal interaction effects. In radio polarimetry observations,
both phenomena may manifest similar features. X-ray data can help to determine
the real origin of the perturbation. We analyse the distribution and physical
properties of the hot gas in the Virgo cluster spiral galaxies NGC 4254 and NGC
4569, which indicate that the cluster environment has had a significant
influence on their properties. By performing both spatial and spectral analyses
of X-ray data, we try to distinguish between two major phenomena: tidal and ram
pressure interactions. We compare our findings with the case of NGC 2276, in
which a shock was reported, by analysing XMM-Newton X-ray data for this galaxy.
We use archival XMM-Newton observations of NGC 4254, NGC 4569, and NGC 2276.
Maps of the soft diffuse emission in the energy band 0.2 - 1 keV are obtained.
For the three galaxies, especially at the position of magnetic field
enhancements we perform a spectral analysis to derive gas temperatures and thus
to look for shock signatures. A shock is a signature of ram pressure resulting
from supersonic velocities; weak tidal interactions are not expected to
influence the temperature of the ionized gas. In NGC 4254, we do not observe
any temperature increase. This suggests tidal interactions rather than ram
pressure stripping. In NGC 4569 the radio polarized ridge shows a higher
temperature, which may indicate ram-pressure effects. For NGC 2276, we do not
find clear indications of a shock. The main driver of the observed distortions
is most likely tidal interaction. Determining gas temperatures via sensitive
X-ray observations seems to be a good method for distinguishing between ram
pressure and tidal interaction effects acting upon a galaxy.

Joint Analysis of Gravitational Lensing, Clustering and Abundance: Toward the Unification of Large-Scale Structure Analysis. (arXiv:1207.2471v1 [astro-ph.CO])

Joint Analysis of Gravitational Lensing, Clustering and Abundance: Toward the Unification of Large-Scale Structure Analysis. (arXiv:1207.2471v1 [astro-ph.CO]):
We explore three different methods based on weak lensing to extract
cosmological constraints from the large-scale structure. In the first approach
(method I), small-scale galaxy lensing measurements of their halo mass provide
a constraint on the halo bias, which can be combined with the large-scale
galaxy clustering to measure the dark matter clustering. In the second approach
(method II), large-scale galaxy clustering and large-scale galaxy-galaxy
lensing can be combined into a direct measurement of the dark matter
clustering. These two methods can be combined into one method I+II to make use
of lensing measurements on all scales. In the third approach (method III), we
add abundance information to the method I. We explore the statistical power of
these three approaches as a function of galaxy luminosity to investigate the
optimal mass range for each method and their cosmological constraining power.
In the case of the SDSS, we find that the three methods give comparable
constraints, but not in the same mass range: the method II works best for halos
of M~10^13 Msun, and the methods I and III work best for halos of M~10^14 Msun.
We discuss the robustness of each method against various systematics.
Furthermore, we extend the analysis to the future large-scale galaxy surveys
and find that the cluster abundance method is not superior to the combined
method I+II, both in terms of statistical power and robustness against
systematic errors. The cosmic shear-shear correlation analysis in the future
surveys yields constraints as strong as the combined method, but suffer from
additional systematic effects. We thus advocate the combined analysis of
clustering and lensing (method I+II) as a powerful alternative to other
large-scale probes. Our analysis provides a guidance to observers planning
large-scale galaxy surveys such as the DES, Euclid, and the LSST.