ABSTRACT:: Fossil systems (FSs) are galaxy associations dominated by a relatively isolated, bright E galaxy. They are characterized by a gap of at least 2 magnitudes between their two brightest galaxies. The properties of FSs are mainly known by numerical simulations, showing that they are extreme systems in which most of their mass was assembled in a short time-scale in the early Universe. Nevertheless, their observational properties are not well stablished. The Fossil Group Origin (FOGO) project is a multiwavelenth study of a large sample of FSs. This project aims to provide conclusive observational properties of FSs. We will show in this talk the main results obtained so far by this project. In particular, we will show the results about the scaling relations of the central galaxies, global X-ray and optical scaling relations, and the galaxy luminosity function properties of these systems. These results provide an observational picture about the formation and evolution of FSs.

ABSTRACT:: Recent studies point to a pivotal transition epoch at high redshift wherein the evolution of galaxies in high density cluster environments shifts from predominately star forming to passively evolving. This transition epoch is, as yet, poorly constrained, in large part due to the need for a statistically significant sample of uniformly selected clusters. In this study, we present an analysis of the star formation activity, derived from Herschel SPIRE observations, of a stellar mass-limited sample of cluster galaxies from z=0.3-1.5 in 274 clusters identified in the IRAC Shallow Cluster Survey (ISCS; Eisenhardt et al.2008) over the 9 square degree Bootes field. The ISCS clusters comprise a uniform sample of ~10^14 solar mass clusters selected as overdensities in three-dimensional space using photometric redshifts. This cluster selection technique is uniquely suited to finding the transition epoch as it does not rely on the presence of a strong red sequence and thus is not biased against actively star forming cluster environments. We derive the average physical properties of individually undetected cluster galaxies, such as the dust-obscured star formation rate and specific star formation rate, as a function of redshift and cluster-centric radius by stacking in the Herschel SPIRE 250um waveband. When compared to a mass-limited sample of similarly selected field galaxies in Bootes, we find that the star formation activity in cluster galaxies rises rapidly compared to the field with increasing redshift, with evidence for enhanced star formation activity in infalling galaxies at large cluster radii. We further examine the role of galaxy mass, type, and AGN content on these results. Additionally, we will present preliminary work on a sample of 11 spectroscopically-confirmed ISCS clusters from z=1.1-1.8 which have been observed with the Herschel PACS 100 and 160um wavebands to a depth of ~100 solar masses per year. These deep observations, when combined with the extensive ancillary data available in the Bootes field, will allow us to examine the full SEDs, including the dust emission peak, of a large sample of infrared luminous cluster galaxies (and field galaxies) as a function of redshift and cluster-centric radius to determine individual galaxy properties as a function of environment as well as constrain the mass assembly epoch of clusters in the ISCS sample.

ABSTRACT:: The determination of the evolution of the metal content of the ICM is confronted with huge difficulties in order to account for the low signal-to-noise ratio of abundance measurements and the upper limits, selection effects, non-Gaussian errors, the intrinsic variety of the objects studied and nstrument-dependent systematics. We present results for the largest sample of clusters to date, 130 (real) clusters at $0.1

ABSTRACT:: From the Gaussian statistics of initial perturbations in the gravitational potential, it is possible to derive the X-ray temperature function of virialised dark-matter haloes without envoking cluster masses. Comparing the theoretical predictions with a numerical simulation, we obtain a good agreement if mass-weighted temperatures are used and the influence of halo mergers on the temperature function is taken into account based on a very simple analytic model.

ABSTRACT: Weighing the Giants has measured high quality weak lensing masses for 51 X-ray luminous galaxy clusters, with a 7% systematic error on the mean cluster mass. This accuracy comes from cosmic-shear-quality data processing, robust photometric redshifts, cross-calibrated mass measurements, and extensive simulations. Combined with a blind analysis approach, these measurements should cut in half the uncertainty on mass proxy calibrations, a critical issue highlighted in recent Planck results. In this talk, I will provide an overview of the Weighing the Giants project and the accuracy of the current measurements. I will present new constraints on non-thermal pressure support in relaxed clusters, and then discuss implications for inter-cluster medium physics and cluster cosmology in light of the new Planck cluster results.

ABSTRACT:: We make an unbiased estimate of radio halo fraction in galaxy clusters to show that these Mpc scale diffuse emissions may be much more numerous than previously thought. Giant radio halos are an important link to our understanding of galaxy cluster mergers, but their powering mechanism and prevalence remain controversial. In Basu (2012) we presented the fist radio-SZ correlation for radio halos to establish the true mass scaling for these objects. In a recent work (Sommer & Basu 2013, subm.) we have used near-identical mass limited samples in the SZ and X-ray, and analyzed radio survey data from NVSS, to show that the number of "off-state" clusters hosting no radio halos is drastically different in the two selection: it is close to 70% in X-rays but consistent with zero in the SZ sample. We offer some qualitative understanding of this difference based on N-body hydrodynamic simulations of cluster mergers, and discuss some implications for the new generation of radio surveys.

ABSTRACT:: The shear amount of observational data on galaxy clusters is extraordinary, especially with influx of newly detected clusters via the thermal Sunyaev-Zel'dovich effect from the ACT, SPT, and Planck experiments. With these large cluster samples the dominant errors in cluster cosmology comes from astrophysical uncertainties and not statistical uncertainties. Simulations offer an avenue to explore the astrophysical properties of the ICM and reduce these uncertainties from "gastrophysics." I will present recent attempts to constrain the ICM properties using simulations and observations, then outline some new challenges for simulations in this post Planck era.

ABSTRACT:: Galaxy clusters that act as strong gravitational lenses are among the rarest objects in the Universe, such that a small fraction of the total galaxy cluster population dominates the global cluster-scale strong lensing cross section. Simulations point toward a host of astrophysical biases that could cause galaxy clusters selected for the presence of bright giant arcs to systematical differ from clusters selected on the other bases, such as mass-proxy observables. I will present results from several recent and forthcoming papers with empirical evidence for/against several specific astrophysical biases in a strong lensing selected sample of galaxy clusters. Specifically, we find no evidence for increased incidence of cool core activity in strong lensing clusters, arguing against the ability of baryonic cooling in evolved clusters to systematically increase the total matter concentrations in their cores. I will also present a direct measurement indicating that orientation bias is a significant driver of large strong lensing cross sections using stacked dynamical observations of strong lensing clusters, as well as the result of a comparison of dynamic and weak lensing mass measurements for a strong lensing selected cluter sample.

ABSTRACT:: The evolution of the temperature distribution function with redshift can be estimated from different cluster surveys. They provide a consistent picture in which the observed temperature distribution function evolved rapidly with redshift. Such an evolution cannot be reproduced in a standard concordance cosmology using standard scaling laws for clusters. I will discuss the implications of these observations and the possible consequence for our knowledge about evolution of the cluster population.

ABSTRACT:: Bent, double-lobed radio sources are frequently (60-70% of the time) found in clusters of galaxies. These radio AGN achieve their swept-back morphologies from ram pressure resulting from the relative motion between the host galaxy and the intracluster medium in which they are embedded. Using data from the 1.4 GHz FIRST and optical SDSS surveys, we have assembled a sample of bent radio sources with optical hosts too faint to be detected in the SDSS. I will present initial results from a Spitzer Snapshot survey to observe 653 of these sources. The survey is revealing hundreds of high-z cluster candidates with redshifts up to z~2. The clusters have a wide range of masses and include those that are undergoing mergers and those that are relaxed. Most of the radio hosts are red, elliptical galaxies, but some (~5%) are luminous quasars. The sample will be used to study galaxy formation and evolution, as well as AGN feedback at high-z, both radio (kinetic) and quasar (radiative) mode.

ABSTRACT:: I will present a recent measurement of the magnetic pressure in cluster outskirts of Coma through Faraday Rotation Measures. I will discuss the dynamical implication of these results, the possible biases in the X-ray estimate of the cluster mass, and the theoretical challenges in explaining this findings.

ABSTRACT:: I present results of our successful optical imaging and spectroscopic searches for distant protoclusters. Targetting blank fields and those of qsos we have identified three systems that show clear strong redshift clustering of Lyman Break galaxies at z=5 consistent with that expected for the initial stages of cluster formation. I describe the results of multi-wavelength follow-up observations designed to explore obscured star formation in the systems. I go on to discuss the prospects for efficient identification of more protoclusters through the targeting of high redshift QSOs and powerful SMGs which are expected to pinpoint massive and therefore clustered dark matter halos at high redshift.

ABSTRACT:: Dark Matter Distribution: A Fully Automated Multiple-Image Finder ALgorithm (MIFAL) and Strong-Lensing Analysis of CLASH clusters. We present an innovative tool for automatically finding sets of multiple images in strong lensing (SL) clusters. We combine an arc-finding algorithm with photometric redshift measurements, along with a parametric mass model, to physically match together multiple-image systems in an automated (''blind'') manner. We obtain accordingly a robust assessment of the likelihood of each arc to belong to one of the multiple-image systems, as well as the redshift of the different systems. These are then used to automatically constrain and refine the lens model to obtain an accurate mass distribution and profile, via a Monte-Carlo Markov Chain (MCMC) with Metropolis-Hastings algorithm. We apply this procedure to perform a case-study SL analysis of CLASH galaxy clusters. Our method and results constitute another step towards fully automating SL analyses as a standard tool for studying cluster mass distributions, and is optimized also for constraining the geometry of the universe or the cosmological parameters from SL clusters. In addition, we find that Bayesian estimates for SL reconstructions can be misleading, due to the strong non-linearity of the lensing phenomena, and propose a natural and simple alternative to choose the best-fit model and errors.

ABSTRACT:: A fraction of massive galaxy clusters host diffuse radio emission in the form of giant radio halos. Such synchrotron sources prove the presence of non-thermal components (relativistic particles and magnetic fields) mixed with the hot Intra Cluster Medium (ICM), whose origin is still matter of debate. In the last years we discover a bi-modal behavior of clusters, according to that behavior merging systems host radio halos while more relaxed systems do not show evidence of diffuse radio emission at the sensitivity level of present radio observations. This behavior together with the fact that radio luminosity of radio halos correlates with the X-ray (thermal) luminosity of the hosting clusters provide important hints on the origin of non-thermal components in galaxy clusters and on their interplay with the thermal ICM. In this talk I will present a revision of the scaling relations between the synchrotron luminosity of radio halos and the thermal properties of the hosting clusters using X-ray, SZ and radio data of a large sample of galaxy clusters. I will discuss how these relations together with a quantitative analysis of the cluster dynamical status can be used to shed light on the origin of giant radio halos and on the interplay between thermal and non-thermal components in galaxy clusters.

ABSTRACT:: The slowly growing number of galaxy "proto-clusters" at z>2 is opening up a new frontier of cluster formation. To address the main factors prohibiting statistical studies of proto-clusters currently, we introduce a simulations-assisted approach that will allow us to study the large numbers of early clusters expected in new surveys. First, we use cosmological simulations to predict the properties of proto-clusters (e.g., size, overdensity, galaxy populations) as a function of redshift and z=0 cluster mass. Next, we construct proto-cluster finders for a range of redshift measurement uncertainties, and calibrate the relation between the observed galaxy overdensities and their z=0 masses. We apply these techniques to identify and characterize a statistical sample of proto-clusters in the COSMOS/UltraVISTA field. Last, we introduce the upcoming HETDEX wide-field Lya emitter survey that will probe a ~6.5 Gpc^3 volume at 1.9

ABSTRACT:: The discovery and properties of the Huge-LQG are discussed. This is the Large Quasar Group (LQG), of 73 member quasars at =1.27, characteristic size (volume^{1/3} 500 Mpc, and longest dimension 1240 Mpc, that is the largest structure currently known in the universe. According to Yadav et al., in the concordance cosmology, there should not be significant deviations from homogeneity on scale larger than 370 Mpc. The Huge-LQG thus challenges the assumption of the cosmological principle. This presentation will also discuss the status of some further LQGs, which, although not so large as the Huge-LQG, nevertheless constitute further challenges to the cosmological principle. Finally, results will be presented on the enhanced occurrence within the LQG environment of a relatively rare type of quasar.

ABSTRACT:: The differences between ellipticals in clusters and the field indicate that galaxies in denser environments formed and assembled their mass earlier. The question is, how did this rapid mass-gain occur? Near their formation epoch, z_f > 2, the differences between cluster and field ellipticals become more apparent. I have compared the properties of galaxies in a sample of protoclusters between 2 which lie above the mass-SFR relation, in protoclusters to the field. I will discuss the insights this study gives us into the different evolutionary paths between cluster and field ellipticals.

ABSTRACT:: In galaxy clusters, galaxies are being rapidly transformed from active star forming galaxies into quiescent, passively evolving galaxies. These transformations are most evident at intermediate redshift where gas-rich galaxies are falling into the clusters for the first time. Unlike low redshift systems where the red sequence dominates the galaxy distribution or high redshift systems where star formation has not yet been quenched; massive, intermediate redshift clusters have the dense environment and hot gas halos to transform their large populations of in-falling star forming galaxies. In the most massive clusters, the transformation appears to include a phase of star bursts for the galaxies falling into the cluster prior to evolving into a more transistional galaxy phase. We use a range of observation of these systems to constrain the transformation that is on-going in the dense cluster environments and to constrain different environmental drivers for the evolution of in-falling galaxies.

ABSTRACT:: We refine methods to identify the Diffuse Stellar Component (DSC) and the Intra-Cluster Light (ICL) in simulations. We apply these methods to the same set of state-of-art hydrodynamical simulations of a large sample of clusters. We analyze simulations run with two different levels of sub-resolution physics: one CSF and another one AGN, which adds also AGN feedback. We find significant differences between the ICL and DSC fractions computed with the two corresponding methods. However, BCG+ICL and BCG+DSC mass fraction are similar. We derive the (brighter) average surface brightness limits that yields, in our simulations. We find that BCGs stellar component, as identified by he dynamical method, are significantly younger and more metal rich than the DSC.

ABSTRACT: We compare the metal abundance distribution in the distant cool-core cluster WARPJ1415.1+3612 at z=1.03 (Santos et al. 2012) to that of a sample of local clusters. We find that the metal distribution in WARPJ1415.1+3612, as measured by Chandra, is comparable to that of the optical light of the associated BCG observed with HST. This is at variance with local systems where the metal distribution is significantly broader than the optical light. We discuss the implications for cluster formation and evolution models of this important result.

ABSTRACT:: We present an innovative approach to underline kinetic Sunyaev-Zeldovich (kSZ) Ef- fect towards cluster of galaxies studying, together with the well tested scaling relation between the thermal SZ brightness, Y, and the cluster total mass, M, a new one wi- th the integrated kSZ, B. The applicability of the suggested approach is checked with synthetic clusters extracted from MultiDark, a Dark Matter (DM) only simulation with 2048 3 particles in a (1 h 1 Gpc) 3 cube. The sample is composed by 345,196 halos with $1\times 10^{13} < M/h^{-1} M_\odot < 1.5 \times 10^{15}$ . The presence of systematics on the integrated kSZ, due to ICM motions, is also considered. Preliminary results on Planck HFI maps of CMB tempe- rature are reported. With the same dataset of synthetic clusters, we explore the kSZ proxy, applied for the first time by ACT team, based on the approach of studying the pairwise momentum of clusters.

ABSTRACT:: The level of star formation (SF) activity in galaxy systems is known to be suppressed relative to the field. According to the well known morphology-density relation and the star formation rate-density relation, in the local Universe high density regions, like groups and clusters, host mostly early type galaxies with lower SF level than field (mostly late-type) galaxies. The environmental dependence of galaxy SF rate may change with redshift, as galaxies in systems undergo significant evolution. Why to study groups in this context? What emerges from recent results is that the largest contribution to the the star formation rate density of the Universe is provided by rather massive galaxies (10^(10) -10^(11) solar masses). Galaxy groups host 70% of massive galaxies at least up to redshift ~1. Thus, it is likely that, if SF rate quenching happens in high density regions, those must be galaxy groups. This seems to be supported by the faster evolution of the SF activity observed in group galaxies with respect to field galaxies since ~1. Thus, to obtain a complete census of the group galaxy population at stellar mass larger than 10^{10} solar masses and of their star formation activity up to redshift ~1, we create a statistical sample of X-ray selected groups up to z~1 in the major blank fields (AEGIS, COSMOS, GOODS and ECDFS) observed also by the infrared Herschel satellite. The aim of the work is to proof whether the membership of a galaxy to a group is sufficient to quench the SF activity of a galaxy. This will show if the structure formation process itself can be one of the major causes of the decline of the SF rate density pf the Universe since redshift 1-2.

ABSTRACT:: The picture of the large-scale structures reveals that the matter in the Universe forms a rich and intricate system, defined as 'cosmic web'. This web contains complex structures as galaxy clusters, filaments, sheets, and large empty voids. In the hierarchical scenario of the gravitational formation process, clusters of galaxies are located at the intersection of filaments and sheets, which are flowing around them. We propose a new method for the cluster mass estimation from the knowledge of the kinematic in the outskirt. At several Megaparsec away from the cluster centre, we might expect to observe galaxy filaments or sheets, whose motion is affected by the presence of the cluster. The gravitational effect of the cluster mass is to perturb the pure Hubble motion, leading to a deceleration. Therefore, the coherent perturbed Hubble flow of galaxies in the outer region of clusters, should allow us to infer the virial mass of the cluster, without even looking at the virialized inner region. We first test the method on a cluster-size halo from Cosmological N-body simulation and then we apply the method on Coma Cluster. We identify two sheets around Coma, and from the observed velocities of the galaxies belonging to the sheets, we measure the virial cluster mass.

ABSTRACT:: I will discuss new observational results on the properties of the X-ray luminous galaxy cluster population in the redshift range $0.8

ABSTRACT:: We present a detailed analysis of the stellar populations of RX J0152.7-1357, a rich galaxy cluster at moderately-high redshift (z\,=\,0.83) with a new set of state-of-the-art tools. With them, we are able to characterize the ages, metallicities, abundance patterns and SFHs of each galaxy individually. We can analyze how these properties are located within the cluster, to disentangle any relation with the local environment. We compare the relations found for ETGs at high redshift with those of a cluster of similar properties at low redshift (Coma) to constrain different evolutionary scenarios. We find that passive evolution stands for the most massive galaxies, whereas low-mass galaxies seem to present a stronger evolution than expected. Most of these low-mass galaxies show more extended SFHs and are located in the outskirts of the cluster. Therefore, we conclude that they have been incorporated into the cluster more recently.

ABSTRACT:: XMM-Newton and Chandra has conducted a number of deep surveys, revealing the sources with unprecedentedly low level of X-ray emission, 10000 times deeper than the limits of RASS catalogs. Those observations, located in data rich fields quickly became our main source of knowledge on how galaxy groups evolve with redshift. I will review the recent results obtained in the COSMOS, AEGIS, CDFS, CDFN and LH fields.

ABSTRACT:: From the observation of a sample of massive clusters of galaxies in the Planck survey, we have statistically detected their Sunyaev-Zeldovich (SZ) effect out to 3 x R500, i.e., a density contrast delta~50-100. Combining the Planck data with XMM-Newton archive data for our whole sample, we have independently reconstructed the underlying thermal pressure profile from the X-ray and SZ observations over the radial range [0.1 - 3] x R500. We provide its precise analytical description assuming a GNFW model. With this work we probe the pressure support in halos far out in their outskirts. This unique observational constraints provides a unique reference to further probe the physical processes at play in clusters external regions (e.g., accretion, thermalisation, non-thermal support, asphericity, clumpiness).

ABSTRACT: Supermassive black holes (SMBHs) play key roles in galaxy evolution. Nowhere is this more clearly seen than in the interactions between SMBH outbursts in the gas rich atmospheres of early type galaxies, groups, and clusters where the SMBH is responsible for maintaining the dichotomy of red and dead galaxies vs. blue, star forming galaxies. From detailed X-ray studies of clusters and groups, we present the properties of typical SMBH outbursts, their evolution, and the energy partition between shocks and the enthalpy of the cavities inflated by the SMBHs. While there is much regularity in the relationship between the SMBH mass and the host galaxy properties (e.g., galaxy velocity dispersion, stellar bulge mass, and halo mass mass), X-ray observations of early type galaxy samples have uncovered notable exceptions that provide insights on the early evolution of the SMBH and the stellar and gaseous components of their host galaxies. The existence of these exceptional galaxies suggests that at very early epochs, the SMBH outbursts are capable of prematurely terminating star formation and driving much of the baryonic content from the dark matter halo. We conclude by describing a future mission that would allow us to understand the evolution of SMBHs and their host galaxies, at the centers of groups and clusters, over cosmological times.

ABSTRACT:: Weak gravitational lensing is a powerful technique to constrain the masses of galaxy clusters in precision cosmology applications. Multiband photometry can be used to reduce some of the biases affecting the cluster mass reconstruction, leading to accurate mass measurements. We describe the dilution of the lensing signal due to the introduction of unlensed sources in the sample used for the shape measurements leading to an underestimation of the cluster mass. We exploit two different approaches for the selection of background lensed sources: the selection in color-color space, choosing an optimal combination of bands, and photometric redshifts. We describe the application of both techniques to realistic simulations of lensing observations (Meneghetti et al. 2010), in order to determine the fraction of unlesed sources in background selected samples. We apply both techniques to perform an accurate mass reconstruction of real galaxy clusters in the redshift range [0.2,0.4].

ABSTRACT:: We analyse the kinematic and chemical evolution of about 150 distant early-type (elliptical and S0) galaxies at 0.2 MOSCA multi-object spectroscopy with intermediate-resolution have been acquired to measure the internal kinematics and stellar populations of the galaxies. From HST/ACS and HST/WFPC2 imaging, surface brightness profiles and structural parameters were derived for half of the galaxy sample. To test the effect on environment, the cluster samples are compared to a representative field galaxy sample at similar redshifts. Kinematic scaling relations indicate a moderate evolution for the whole galaxy population in each density regime, whereas their stellar populations show a more complex picture. In all environments, S0 galaxies show a faster evolution than elliptical galaxies. For galaxies in clusters a slight radial dependence of the evolution out to one virial radius is found. Dividing the cluster samples with respect to their mass, a mass dependent evolution with a stronger evolution of lower-mass galaxies (M

ABSTRACT:: We study the heating of the cool cores in galaxy clusters by cosmic-rays (CRs) accelerated by the central active galactic nuclei (AGNs). We especially focus on the stability of the heating. The CRs stream with Alfven waves in the intracluster medium (ICM) and heat the ICM. First, assuming that the heating and radiative cooling is balanced, we search steady state solutions for the ICM and CR profiles of clusters by solving a boundary value problem. The boundary conditions are set so that the solutions are consistent with observations of clusters. Then, we analyze the stability of the solutions via a Lagrangian perturbation analysis and find that the solutions are globally stable. We confirm the results by numerical simulations. Using the steady state solutions as the initial conditions, we follow the evolution of the profiles for 100 Gyr. We find that the profiles do not evolve on time scales much larger than cluster lifetimes. The main reason of the stability is that CRs stream in the ICM and the heating is not localized around the AGN. These results, as well as consistency with observations of radio mini-halos, suggest that the CR heating is a promising mechanism to solve the so-called ``cooling flow problem''.

ABSTRACT:: With >900 orbits, the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) is the largest Hubble program ever approved. It consists of a WFC3/ACS imaging survey of 5 fields (Goods-N/S, UDS, COSMOS and ERS). Observations, started in mid 2010, will be finalized in mid 2013. We have derived photometric redshifts from the optical-to-midIR multiwavelength catalogs currently being built up in the different CANDELS fields (Galametz et al. 2013 for UDS) and have conducted a search for intermediate-to-high redshift large scale structures and galaxy clusters. The CANDELS fields are known to host galaxy groups at high-redshift e.g., at z~1.6 in GS (Kurk et al. 2008) and UDS (Papovich et al. 2010, Tanaka et al. 2010). We will present new structures at z>1.4. We will also introduce our study on the AGN fraction in these different galaxy structures along with an analysis of dependence of other galaxy properties (e.g., stellar masses, morphology, colors) with environment (e.g., field vs. groups vs. clusters) at high-redshift.

ABSTRACT:: Using 3D AMR hydrodynamic simulations with a dynamical range up to 10 million, we study the impact of thermal instability in the evolution of the intracluster medium. Moderate turbulence of few 100 km/s leads to the growth of nonlinear thermal instability within the central few tens kpc. In the presence of global heating, the condensation of filamentary cold gas is violent, occurring when t_cool/t_ff < 10. The stochastic inelastic collisions between the cold clouds and the clumpy torus, promote angular momentum cancellation, boosting the accretion rate up to 100 times the Bondi rate. In a turbulent and heated atmosphere, the mode of accretion is cold and chaotic. The cooling rate is thus a good approximation to the accretion rate. As shown by long-term simulations, chaotic cold accretion is crucial to self-regulate mechanical AGN feedback, which can avoid the cooling catastrophe and reproduce key observed features of galaxy clusters, as cavities, shocks, metal uplift, and turbulence.

ABSTRACT:: Larger galaxy cluster surveys put several constrains on average properties of galaxy clusters, such as richness, BCG, red Sequence, projected number density profile, luminosity distribution etc. Taken informations from these surveys a model will be introduced, which accounts for the afore mentioned properties, and thus depicts a realistic galaxy cluster (in the optical filter bands). Given this model a filtering function is constructed which allows for optimal searching for galaxy clusters. Optimal means that an unbiased signal estimate and a minimal variance are enforced.

ABSTRACT:: The Massive Distant Clusters of WISE Survey (MaDCoWS) is a comprehensive program to detect and characterize the most massive galaxy clusters in the Universe at z>1 over the full extragalactic sky. The foundation for MaDCoWS is data from the NASA Wide-field Infrared Survey Explorer (WISE) mission. Results from our multi-wavelength followup program have proven that WISE is deep enough to identify massive z>~1 clusters as overdensities of L>L* galaxies that are red in the two bluest passbands. I will give an overview of the survey, including the motivation and search method, and will present the latest results from our followup efforts. In addition, I will show preliminary results from extending MaDCoWS using data from AllWISE, a project to combine the data from WISE's cryogenic and post cryogenic mission phases, resulting in a catalog ~twice as deep as the WISE All-Sky Release.

ABSTRACT:: Cold fronts in cool core clusters are thought to be induced by minor mergers and to develop through a sloshing mechanism. While temperature and surface brightness jumps have been detected and measured in many systems, a detailed characterization of the metal abundance across the discontinuity is only available for a handful of objects and is an important missing piece of the puzzle. Moreover, since sloshing may redistribute metals throughout the intracluster medium, heavy elements may be used to trace motions of the gas. Thus, the distribution of metals into clusters hosting cold fronts represents a very powerful mean to study the sloshing process. We present results from the analysis of a long (120 ksec) XMM-Newton observation of the galaxy cluster A496 focussing on the metal distribution in this cluster and its correlation with the cold fronts.

ABSTRACT: Ultra-compact and massive galaxies at high--redshift offer the opportunity to test some of our key ideas on galaxy evolution. These are the first galaxies in the universe to quench star formation, and their large stellar mass and extreme stellar density strongly suggest that they primarily formed through a highly dissipative mechanism, with hierarchical merging of sizeable stellar systems being comparatively unimportant. We identified their likely progenitors when they were still star forming at redshift z>3 and found evidence that their stellar populations are on average older than other non-compact star-forming galaxies of similar mass at the same epoch, indicative of an accelerated evolution. While ultra-compact galaxies dominated the population of passive and massive galaxies at high redshift, after reaching a peak of abundance at redshift around 1, they are absent in the local universe. By looking at the differential evolution of these structures in environment of different densities, such as groups and clusters spanning a range of richness and mass, we discuss possible evolutionary meachanisms that might have led to their apparent disappearance.

ABSTRACT:: While the build-up of large structures, such as galaxy clusters, from the earliest epochs to the present day has been extensively studied with cosmological simulations, the early formation and evolution of their galaxy content, and its relation to the transformation of the host environment, are still somewhat poorly understood. Recently, a series of discoveries in at z~2 have started to bridge the gap between the massive structures of the last 9 Gyr and the vigorously active protoclusters of the early Universe, finding intermediate structures that allow us to study the coevolution of cluster galaxies and their host structure very close to their formation epoch. This breakthrough has been made possible thanks in part to sophisticated space-based instruments and in particular near-infrared spectroscopy with Hubble. I will discuss the characteristics of the galaxy population in the most distant cluster confirmed so far, at z=2, and examine the possibilities offered by future missions.

ABSTRACT:: Galaxies at the centers of clusters grow through a combination of in situ star formation, major mergers, the accretion of less massive galaxies, and possibly a substantial contribution stripped from globular clusters. The stars that come from these various sources wind up at different radii, have different chemical signatures, and wind up with kinematically distinct orbits. Thus spatially-resolved studies of the kinematics, stellar population properties, and detailed chemical abundance patterns of stars in local massive galaxies contain the imprint of their origins. We present the results of a detailed study of gradients in M87. These include not only gradients in age, metallicity, and alpha-element enhancement, but the abundance patterns of multiple light elements, and detailed orbital structure extracted from 3D Schwarzschild modeling. These are compared with the kinematics and chemical abundance patterns of the M87 globular cluster system, as well as expectations for in situ and accreted stellar populations. The combined data suggest three distinct radial 'zones' in M87; in each of these, the stellar population is dominated by stars from different sources.

ABSTRACT:: In my talk, I will show how the extraordinary multi-wavelength data set of the CLASH survey can be used to decouple, for the first time over more than three decades in radius, the dark-matter distributions in galaxy clusters and to measure dark-matter profiles, in particular the values of the inner slope, offering a fundamental test of the predictions of the LambdaCDM scenario. CLASH is a 524-orbit HST Treasury Programme targeting X-ray-selected massive clusters of galaxies in 16 broadband filters, from the near-UV to the near-IR. Thanks to the unique observations of our photometric and spectroscopic campaigns, I will illustrate how it is possible to select reliably the cluster members, model accurately their spectral energy distribution and surface brightness and estimate the cluster cumulative mass profiles in the form of stars out to approximately 3 Mpc from the cluster centres. Taking advantage of the unparalleled multi-diagnostics (strong lensing, weak lensing, dynamical, X-ray) mass measurements of my CLASH collaborators, I will present the first results on the estimates of the cluster dark-matter distributions by subtracting the stellar and hot gas from the total mass components. Moreover, I will show how measured stellar velocity dispersion profiles of brightest cluster galaxies will be employed to perform refined dynamical analyses, allowing tighter constraints on the inner shape of the cluster dark-matter haloes.

ABSTRACT:: One of the longest-standing problems in extra-Galactic astronomy is the emergence of the red sequence of galaxies. Made up of predominantly passively-evolving systems, the origin of the red sequence is a problem that has never been fully answered. We are now in the era of exquisite multi-wavelength surveys and able to tackle this problem in ways that were not previously possible. With its unique K-band depth and Spitzer coverage (plus very deep data at shorter wavelengths) the UKIDSS Ultra-Deep Survey (UDS) is the ideal survey for studying the z~2 universe, and in particular the few faint, passive objects that exist at this redshift. This epoch is crucial for study as it is when the first significant populations of passive galaxies are observed. Using measurements of the large-scale structure of such samples I will show where these galaxies are located in the Universe (i.e. their host dark matter halo mass) and what this can tell us about the process of transformation from star-forming to passive.

ABSTRACT:: The Atacama Cosmology Telescope (ACT) has conducted a survey at millimetre wavelengths with arcminute resolution in order to search for galaxy clusters using the Sunyaev-Zel'dovich (SZ) effect. In this talk, I present results from the ACT SZ survey after three observing seasons, and describe measurements of cosmological parameters based on cluster counts as a function of redshift, including a $< 0.29$ eV limit on the sum of the neutrino masses. I will discuss how the assumption of different cluster physics models affects these results.

ABSTRACT:: The mass assembly of the most massive galaxies in the universe is still an open issue. Recent works have reported a strong size and mass increase of massive bulge dominated galaxies over the last 10Gyrs. The physical mechanisms behind these growths are not constrained yet. Is the evolution dominated by in-situ processes such as AGN feedback and/or star formation or by external processes like major/minor mergers? Answering these questions requires a detailed study of the structure of these massive early-type galaxies at different epochs living in different environments. I my talk I will therefore show how the structural properties of massive ETGs living in clusters, groups and in the field evolve from z~1.5 to present. I will then discuss how our observational results compare with different state-of-the-art hierarchical models and how this information can be used to put constraints on the physics leading to the assembly of these objects.

ABSTRACT:: The Planck experiment allows to construct the first all-sky map of the thermal Sunyaev-Zeldovich (tSZ) effect by applying component separation algorithms to the 100 to 857 GHz frequency channel maps. These maps show a clear galaxy cluster tSZ signal that is well matched with blindly detected clusters in the Planck SZ catalogue. To characterize the signal in the tSZ map we have computed its angular power spectrum. We have carefully modelled and subtracted forgrounds residuals, mainly thermal dust and CIB, to the tSZ power spectrum. The measured tSZ power spectrum is consistent with that expected from the Planck catalogue of SZ sources, with additional clear evidence of signal from unresolved clusters and, potentially, diffuse warm baryons. We used the tSZ power spectrum to obtain the following cosmological constraints on $\sigma_{8}$.

ABSTRACT:: In the Chandra Large Project ERA (Environments of Radio-loud AGN), we have characterised the cluster environments of a sample of 26 radio-loud AGN at $z \sim 0.5$ that covers three decades of radio luminosity. This is the first systematic X-ray environmental study at a single epoch, and has allowed us to examine the relationship between radio luminosity and cluster environment without the problems of Malmquist bias. We will present evidence for a correlation between radio luminosity and host cluster X-ray luminosity, as well as tentative evidence that this correlation is driven by the sub-population of low-excitation radio galaxies. We are now comparing our $z \sim 0.5$ sample with a sample of radio galaxies at $z<0.1$ to look for evidence of evolution with epoch. We will present our preliminary findings and discuss the implications of our results for AGN feedback in galaxy formation models and cosmological simulations.

ABSTRACT:: With the aim of understanding the effect of the environment on the evolving galaxy population, we have carried out a Blind Ultra Deep HI Environmental Survey (BUDHIES). Using the Westerbork Synthesis Radio Telescope (WSRT) we have detected HI in hundreds of galaxies in and around two Abell clusters at z~0.2. The observations cover a very large volume, sampling a wide range of environments that includes voids, groups, forming clusters and massive virialized clusters. Our study combines, for the first time, optical and IR properties with HI content at a redshift where evolutionary effects begin to show. In particular, this talk will focus on the impact of environment (and stellar mass) on star-formation, morphology and HI in galaxies beyond z=0.

ABSTRACT:: We investigate the physical processes involved in the development of the red sequence (RS) of cluster galaxies by using a combination of cosmological N-body simulations of clusters of galaxies and a semi-analytic model of galaxy formation. Results show good agreement between the general trend of the simulated RS and the observed colour-magnitude relation (CMR) of early-type galaxies in different magnitude planes. However, in many clusters, the most luminous galaxies (MR major wet mergers are relevant in determining the properties of less luminous galaxies. Since the most luminous galaxies have a narrow spread in ages, their metallicities are the main factor that affects their colours. Their mean iron abundances are close to the solar value and have already been reached at z=1. This fact is consistent with several observational evidences that favour a scenario in which both the slope and scatter of the CMR are in place since z =1.2. Galaxies in the bright end reach an upper limit in metallicity as a result of the competition of the mass of stars and metals provided by the star formation occuring in the galaxies themselves and by the accretion of merging satellites.The effect of dry mergers is to increase the mass of galaxies in the bright end, without significantly altering their metallicities. Hence, very luminous galaxies present similar colours that are bluer than those expected if recent star formation activity were higher, thus giving rise to a break in the RS. These results are found for simulated clusters with different virial masses ($10^{14} − 10^{15}$ h$^{−1}$M⊙), supporting the idea of the universality of the CMR in agreement with observational results.

ABSTRACT:: We are carrying out a systematic low frequency (610-235 MHz) radio survey of 67 luminous galaxy clusters in the redshift range 0.2-0.4, called the Extended GMRT Radio Halo Survey. The aim of this survey is to search for diffuse, extended radio emission termed as 'radio halos' and 'radio relics' associated with the relativistic electrons and magnetic fields distributed on ~Mpc scales in the intra-cluster medium (ICM). Radio halos and relics in galaxy clusters are tracers of turbulence and shocks associated with the recent dynamical history of the cluster. I will present recent results on the radio properties and occurrence fractions of radio halos in these clusters. The implications of these results in the context of evolution of merging galaxy clusters will be discussed.

ABSTRACT:: We calibrated a scaling relation between weak lensing masses and X-ray spectroscopic temperatures for a sample of 10 galaxy groups in the COSMOS field and 25 clusters from litterature. Our sample expands weak lensing calibrated M-T relations to a lower mass and temperature range than previous studies. We obtained a slope consistent with the self-similar prediction, conflicting with previous galaxy group studies using hydrostatic mass estimates. We interpret this discrepancy as a deviation between hydrostatic and lensing masses, which is indicated by simulations. Our study provides the first observational support for this scenario.

ABSTRACT:: X-ray observations of galaxy clusters provide emission measure weighted spectra, arising from a range of density and temperature fluctuations in the intra-cluster medium (ICM). This is fitted to a single temperature plasma emission model to provide an estimate of the gas density and temperature, which are sensitive to the gas inhomogeneities.

ABSTRACT:: The discrepancy between the observed and predicted strong lensing properties of galaxy clusters present a source of tension for LCDM cosmology. We study the relationship between Einstein radii, X-ray luminosities and inferred masses, comparing high-z observations and predictions from hydrodynamic simulations that include --- along with other baryonic processes --- star formation, chemical evolution, supernovae and AGN feedback. We discuss the impact of baryonic physics, cluster selection criteria (X-­ray flux, mass and/or dynamical state), mass modelling, and the large (mock) sample­-to-­sample variation due to triaxiality.

ABSTRACT:: Our Mahalo-Subaru project has been mapping out star forming activities at the peak epoch of galaxy formation in some proto-cluster candidates and in a general field (SXDF-UDS-CANDELS) at $1.52$ traced by many Halpha emitters on top of continuum selected cluster member candidates. These serve as ideal laboratories for us to investigate the impact of environments upon galaxy formation processes, such as star formation and AGN activities driven by galaxy-galaxy interaction. By comparing the properties of star forming galaxies with those in the general field at z~2, we address how the progenitors of present-day cluster early-type galaxies form and evolve along with the growth of clusters themselves. We find that galaxies in high density environments tend to be more masive, bursty and dusty, suggesting a biased galaxy formation involving dusty star formation activities.

ABSTRACT:: X-ray observations of hot gas in galaxy clusters often show steeper temperature gradients across cold fronts -- contact discontinuities, driven by the differential gas motions. These sharp (few kpc wide) surface brightness/temperature discontinuities would be quickly smeared out by the electron thermal conduction in unmagnetized plasma, suggesting significant suppression of the heat flow across the discontinuities. In fact, the character of the gas flow near cold fronts is favorable for suppression of conduction by aligning magnetic field lines along the discontinuities. We argue that a similar mechanism is operating in the bulk of the gas. Generic 3D random isotropic and incompressible motions increase the temperature gradients (in some places) and at the same time suppress the conduction by aligning the magnetic field lines perpendicular to the temperature gradient. We show that the suppression of the effective conductivity in the bulk of the gas can be linked to the increase of the frozen magnetic field energy density. On average the rate of decay of the temperature fluctuations d/dt decreases as ^(-1/5).

ABSTRACT:: We explore the role of environment in the evolution of galaxies in $0.1

ABSTRACT:: Our project is related to two fundamental questions of modern extragalactics: mass assembly and star formation as a function of environment. We tackle these issues by measuring stellar population properties and galaxy structures in clusters of different masses at their early assembly phase. We investigated the field of the gravitational lens MG2016+112 through narrow-band IR imaging, tracing H_alpha emitters in overdensities at z=0.6 and z=0.8. These show strikingly high SF-rates in comparison to the field. This might indicate the early cluster assembly phase with enhanced galaxy interaction in transition environments. Interactions inducing SF are favored in low mass haloes where clumps are accreted into clusters, and groups drive the properties. We link these measurements to our analysis of massive clusters of the CLASH survey where we exploit multi-wavelength HST/ACS imaging and VIMOS multiplex spectroscopy for an analysis of structure, SF, AGN activity, morphology and stellar population.

ABSTRACT:: Some recent observational studies of moderate-redshift ($z\lesssim0.6$) galaxy groups and clusters have come to the surprising conclusion that the gas mass fraction within $r_{500}$ increases relatively rapidly with redshift, while the stellar mass fraction shows little or no evolution. To investigate the physical origin of these trends, we use a new suite of large cosmological hydrodynamical simulations (which form an extension of the OverWhelmingly Large Simulations) with varying 'sub-grid' physics. We find that only models which include ejective AGN feedback at high-redshift (in 'QSO' mode) are able to reproduce the observed evolution of the gas and stellar mass fractions. The same class of models were previously shown to reproduce the $z=0$ properties of X-ray groups. We discuss the important consequences that a rapidly varying baryon fraction has for the use of clusters as probes of cosmology.

ABSTRACT:: We investigate the baryon distribution in 37 groups and clusters based on XMM-Newton, Chandra and SDSS-DR8 data covering a range of 1 measured within R2500 and R500. We confirm the previous trend found in the literature: the star formation efficiency is lower in more massive clusters; it decreases by an order of magnitude from groups to clusters inside both R2500 and R500. We also observe a decrease of the cold baryon fraction as well as a decrease of the star formation efficiency from inside out. This suggests that galaxies in more massive clusters have their gas reservoir more affected by mechanisms that quenches star formation. The stellar mass fraction inside R2500 and R500 increases towards low-mass systems faster than the decrease of the gas fraction; therefore the total baryonic fraction increases with cluster mass. The contribution of intracluster light - still badly constrained - to the total baryon budget cannot account for the observed trend.

ABSTRACT:: Galaxy clusters often exhibit X-ray morphologies suggestive of recent interaction with a subcluster. A3376 is a nearby massive cluster whose bullet-shaped X-ray emission indicates a recent collision. It displays a pair of Mpc-scale radio relics and its BCG is located 970kpc away from the peak of X-ray emission. In order to recover the dynamical history of A3376, we perform a set of N-body hydrodynamical simulations. By attempting to match X-ray morphology, temperature, virial mass and X-ray luminosity, we set approximate constraints, namely: mass ratio, relative velocity, impact parameter, gas concentration, inclination and age. We thus propose a specific scenario for the merging event of A3376 accounting for several of its features. We are also able to explain the Mach number of the shock. From this scenario a specific prediction arises, concerning the distribuition of dark matter. Future weak lensing analysis might either help corroborate this picture or overthrow it.

ABSTRACT:: For given observational Sunyaev-Zel'dovich and X-ray emission data from massive galaxy clusters we present a non-parametric reconstruction method for the lensing potential. We explain the physical details and assumptions the method is based on and explain how the numerical algorithm itself is implemented with a Richardson-Lucy algorithm as a central engine. We test our method by simulating Sunyaev-Zel'dovich observations with ALMA and observations of thermal X-ray emission with Chandra. In order to do so we simulate a galaxy cluster with a spherically symmetric NFW density profile filled with gas in hydrostatic equilibrium, from which we derive the observables. We achieve a relative accuracy of about 5% (SZ) and 2% (X-ray) up to a given radius. The ultimate goal is a non-parametric method combining strong and weak lensing, observational signatures of thermal gas physics and galaxy kinematics into one consistent model for the projected cluster potential.

ABSTRACT:: We compare X-Ray observations of galaxy clusters with both SPH and AMR non-radiative simulations to estimate the amount of energy feedback in galaxy clusters, especially within cluster cores. We connect the energy feedback with the thermodynamic entropy of the intra-cluster medium (ICM) to compute the non-gravitational energy contained in the ICM. We find the energy feedback scales with the cluster temperature from groups to cluster scales with relatively small scatter. We also study the correlations of the energy feedback with other observed/estimated cluster quantities and especially with cluster core radio luminosity. Apart from estimating the non-gravitational energy per particle, with agreement with previous estimates, we also find the energy feedback "profiles" upto r500. The profiles differ significantly between cool-core and non cool-core clusters. We argue that any feedback mechanism utilized in hydro simulations or semi-analytical modelling of clusters must conform to these profiles to reproduce `real' clusters', which is crucial for calibrating clusters for cosmology.

ABSTRACT:: We present results from the Planck satellite studies of the peculiar motions of X-ray galaxy clusters induced by the kinetic Sunyaev-Zeldovich effect (kSZ). Using the galaxy cluster X-ray MCXC catalogue, three types of constraints are studied by implementing different filters that target the kSZ generated at the clusters' angular positions: 1) the clusters' radial peculiar velocity average, 2) clusters' radial peculiar velocity rms, and 3) clusters' kSZ dipole and bulk flow amplitude at different depths. These investigations provide a test against the predicted peculiar velocities from LambdaCDM and a different view of a long ongoing debate on the amplitude of the local bulk flow in the vicinity of the Local Group.

ABSTRACT:: We present preliminary results on the angular correlation functions of 1which covers 100 contiguous square degrees with IRAC CH1&CH2 photometry ([4.5]um=21.7(AB)). These two bands allow us to select galaxies in redshift and estimate stellar masses above ~1e10 Msun. Our correlation functions probe a range of separations from 9 arcseconds to 4 degrees with high count statistics. We analyze them in terms of the halo occupation framework, finding the typical halo masses that host central and satellite galaxies for a range of samples selected in stellar mass. We also compute the relation between halo and central stellar mass and determine the peak of stellar mass efficiency.

ABSTRACT:: TBD

ABSTRACT:: We propose to present results of the analysis of galaxy properties in the CFHTLS clusters detected by Durret et al. 2011. We will show the evolution of the Red Sequence in composite clusters stacked by (photometric) redshift bin. The RS is clearly detected up to redshift of 1 in the r-z/z colour magnitude diagram and its evolution is shown to bein good agreement with BC03 predictions with a redshift of formation zf=3. The evolution of luminosity functions will be discussed, comparing that obtained for galaxies within the RS to a membership selection based on photometric redshifts.

ABSTRACT:: We employ a large sample of 20,000 groups and clusters around Luminous Red Galaxies in the SDSS to investigate how the stacked stellar mass fraction varies with total mass, M500, in these systems. Our total mass estimates are demonstrated to be highly accurate on average when compared with stacked velocity dispersion and lensing measurements. We find that the stellar mass fraction depends only weakly on total mass and that the contribution of intracluster light to the total stellar mass fraction of groups and clusters is large (typically ~50 per cent) but does not depend significantly on system mass. Both of these findings are in accordance with the predictions of cosmological simulations. When combined with observed hot gas mass fractions, our results imply that galaxy groups have significantly lower baryon fractions than massive clusters. Ejection of gas due to energetic AGN feedback provides a plausible mechanism for explaining the trends we observe.

ABSTRACT:: I present the first results from an X-ray survey of the >80 most massive galaxy discovered with the South Pole Telescope, spanning 0.30.75. We interpret this evolution as being due to the inability of the cooling flow to cool below temperatures of ~10^6K. Instead, this gas "piles up" in the center of the cluster, maintaining a constant minimum entropy of ~10 keV cm^2 over the past ~10 Gyr. The lack of strong cool cores at z>0.75 mean that the Universal profile of galaxy clusters becomes even better defined at high redshift, making these clusters excellent tools for cosmological studies.

ABSTRACT:: The galaxy cluster MACS\,J0717.5+3745 ($z=0.55$) is the largest known cosmic lens, with complex internal structures. I present a complete weak and strong-lensing analysis of its mass properties from wide-field Subaru/Suprime-Cam and high-resolution Hubble Space Telescope ({\it HST}) observations taken as part of CLASH. A unique combination of consistent weak-lensing shear, magnification and strong-lensing allows an accurate radial mass profile of the cluster and its surrounding large-scale structure to be reliably derived out to 5 Mpc/h. The central non-parametric lensing map reveals the internal dark matter substructure is overall consistent with the light. The wide-field weak-lensing mass map reveals a clear filamentary structure traced by distinct mass halos. The total mass of the cluster as determined by several methods is Mvir=(2.8+/-0.4)*10^{15}M_sun, making it the most massive cluster known beyond z>0.5, albeit still marginally within LCDM realm.

ABSTRACT:: The Cluster Progenitor Survey (CPS) is a systematic study of galaxy formation and cluster progenitor assembly using a sample of approximately 100 Virgo-sized clusters at 1.0 ift and is not dependent on galaxy star-formation history. Cluster progenitors are selected from a deep, 28 sq.deg Spitzer exploratory field taken as part of the Spitzer/HETDEX Large Area (SHELA) survey, located within the SDSS Stripe 82 and Dark Energy Survey regions. This data is sensitive to cluster galaxies down to M(4.5um)*+2 mag and cluster progenitors to halo masses of ~3 x 10^13 h-1 Msolar, and comprises a highly homogeneous dataset that minimizes observational biases. We present the properties of our cluster catalog and discuss implications for the progenitors of present-day Virgo-sized objects.

ABSTRACT:: We believe elliptical galaxies formed the bulk of their stellar population in dense regions at a redshift of z~2.5-3, and then evolved passively up to the present. At these same redshifts, galaxy clusters are assembling to form the massive structures observed today. We discuss our recent results on the properties of galaxies in clusters from z~2 to the present, in terms of morphological evolution and the evolution of galaxy scaling relations. In particular, we will present our work on the evolution of early-type sizes and the mass-size relation, as well as on the quenching of star formation.

ABSTRACT:: We have stacked deep FORS1 spectra of the ICL in a cluster at z=0.29 to investigate the intergalactic stellar populations. We find that most of the ICL stars are old and metal rich, at odds with what seems to be observed in Virgo and Hydra. We will discuss possible scenarios to explain the discrepancy in terms of the galaxy formation history in clusters.

ABSTRACT:: We have reached the era where microwave surveys such as the Atacama Cosmology Telescope (ACT), the South Pole Telescope (SPT) and Planck are reporting the first samples of massive galaxy clusters through the Sunyaev-Zel'dovich (SZ) effect. In this talk I will introduce a new set of optically-confirmed high redshift galaxy clusters discovered by ACT through the SZ effect observations since 2008 as well as our ambitious program to identify and characterize the galaxy clusters using a plethora of multi-wavelength observations (Chandra, XMM, Spitzer, Hubble, Gemini and VLT). As part of this program I will discuss our discovery of "El Gordo" as the most massive and hottest (X-ray) cluster known in the distant universe and its implications within the LCDM framework. I will also discuss our large program aimed to calibrate the different mass scaling relations for clusters necessary to exploit their counts as a function of mass and redshift to probe of structure growth and cosmology.

ABSTRACT:: We derive the bar fraction in three different environments: field, Virgo, and Coma clusters, covering an unprecedentedly large range of galaxy luminosities. We also show that the difference between the bar fraction distributions in the field and Coma Cluster is statistically significant, with Virgo being an intermediate case. We interpret this result as a variation of the effect of environment on bar formation depending on galaxy luminosity. We speculate that brighter disk galaxies are stable enough against interactions to keep their cold structure, thus, the interactions are able to trigger bar formation. For fainter galaxies, the interactions become strong enough to heat up the disks inhibiting bar formation and even destroying the disks. Finally, we point out that the controversy regarding whether the bar fraction depends on environment could be resolved by taking into account the different luminosity ranges probed by the galaxy samples studied so far.

ABSTRACT:: I will focus on what we have learned from simulations about the uncertainties in the lens modeling. I will discuss recent results on masses and mass profiles as well as on local estimates of lens properties such as the deflection field and the lensing magnification. I will also show the results of some comparisons between mass modeling techniques using simulated data.

ABSTRACT:: I will show results of the analysis of the galaxy population properties in the cluster MACSJ1206.2-0847 at redshift z~0.44, on the basis of spectral classification of ~600 member galaxies and the analysis of luminosity functions (LFs) and colors based on SUBARU optical data. The primary objectives of this analysis are: the study of the relation between cluster dynamics and properties/evolution of the stellar populations and the study of the effect of the cluster environment on the properties of galaxies. First results suggest that galaxy populations are both spatially and dynamically segregated. Moreover the cluster is elongated in NW-SE direction, indicating that MACSJ1206 is not fully relaxed.

ABSTRACT:: Radio Halos in galaxy clusters have been observed using various high resolution telescopes such as the VLA, and significant progress has been made in understanding their properties and dynamics. Yet the powering mechanism responsible for the radio emission is still unknown, and systematic studies of these sources are rare. High sensitivities that will be achieved with MeerKAT and SKA will enable researchers to test the existing models of radio halo origin and a deeper understanding of these sources. As a first step in that direction we present preliminary results obtained from radio observations of 8 known clusters which were carried out using the KAT7, a precursor array to the MeerKAT and SKA. All the sources are detectable with KAT7, albeit at a low resolution (3.6 archmin).

ABSTRACT:: "The existence of the strong mass segregation observed at least up to $z \sim 1$ in the dense environment, would suggest that the galaxy stellar mass function (GSMF) depends on the environment. From the theoretical point of view, also semi-analytical models suggest that galaxies born with the same stellar mass can end up with quite different stellar masses in different environment since the galaxy evolution and its environment are are strongly coupled. For this reason, in this work we investigate whether and how the effects of mass and environment are related and whether the environment can influence the galaxy masses themselves. In particular, we will consider the galaxy stellar mass distribution in different environments. We construct a sample of X-ray selected groups and clusters at z < 0.5 in the COSMOS and CFHTLS fields, spanning a total mass range from $10^{13}$ to $5\times 10^{14}$ solar masses. We define two additional environments on the basis a density parameter estimate to distinguish isolated galaxies and "filament like galaxies" located in regions of high density but not belonging to any X-ray extended emission. The comparison of the GSMF in these environments is then compared with the predictions of the Millennium Simulation."

ABSTRACT:: In the first part of my presentation I will illustrate how the outer regions of cluster can be characterized by combining surface brightness profiles from ROSAT with pressure profiles from Planck. In the second part I will show how the full potential of upcoming SZ experiments, such as SPT3g and CCAT, can be reached only by complementing radio observations with X-ray measurements from a dedicated, low cost, X-ray mission.

ABSTRACT:: The kinematic SZ effect has only recently, and tentatively, been detected on resolved scales in an individual cluster, using Bolocam 1mm and 2mm observations of MACS0717.5+3745. I will discuss further observational constraints on the peculiar velocities of the subcluster components in this cluster using newly obtained SCUBA-2 850 micron and deeper Bolocam 1mm observations.

ABSTRACT:: We compute the mass and velocity anisotropy profiles of Abell 2142 and, from there, the pseudo phase space density profile and the density slope - velocity anisotropy relation, and compare them with theoretical expectations. We will discuss the deviations that we find from the theoretical relations.

ABSTRACT:: We study the properties of the brightest galaxies (BCGs) in compact (CGs) and loose groups (LGs) of galaxies to deepen our understanding of the physical mechanisms acting upon galaxy evolution in different environments. We compare a number of physical properties of the BCGs in Cgs and in subsamples of LGs defined by their mass and total luminosity, namely: absolute magnitude, color, size, surface brightness, stellar mass, concentration and morphological information from the Galaxy Zoo. Some properties of the BCGs in CGs are comparable to those of BCGs in average LGs. However, BCGs in CGs are systematically more concentrated and have larger surface brightness than their counterparts in both, high and low mass Lgs. When comparing BCGs in subsamples of CGs and LGs selected to have similar luminosities, we find that BCGs in CGs are, on average, brighter, more massive, larger, redder and more frequently classified as ellipticals than BCGs in LGs. We find that, compared to BCGs in LGs, BCGs in CGs contain a larger fraction of the system's total luminosity and differ more in absolute magnitude with the second ranked galaxy. We have shown in a previous work (Coenda et al.), that the overall galaxy population in CGs have undergone a major transformation compared to LG galaxies. In this work we find that their BCGs also differ. Some mechanisms responsible of transforming late type galaxies into early types, such as mergers, could be more effective within compact groups due to their high densities and small velocity dispersions, thus leading their BCGs along somewhat different evolutionary paths.

ABSTRACT:: Recent work from field galaxy surveys has suggested that the star-formation-density relation seen in the local universe may reverse at z ~ 1. These results are difficult to reconcile with the predictions of hierarchical models of galaxy evolution. Using new data from the GCLASS survey, a large spectroscopic survey of ten rich clusters at z ~ 1, I will show that the star-formation-density relation seen in the local universe is clearly not reversed in the highest-density environments at z ~ 1. I will also discuss the differences between the stellar populations of cluster and field galaxies. One of the most intriguing results of that comparison is that the specific star formation rates of star forming galaxies (at fixed stellar mass) are identical in both the cluster and field environments. This independence suggests that environmentally-driven quenching of star formation must be a rapid process. The GCLASS clusters also show a significant excess of post-starburst galaxies compared to the field, which further supports the interpretation of rapid timescale of environmentally-driven quenching.

ABSTRACT:: Although the massive core Red Sequence of galaxy clusters is thought to have formed at redshifts greater than 1.5, many galaxies, especially of intermediate to low stellar mass, were transitioning from star-forming late-types and irregulars to passive early-types at z = 1. Here we use VLT FORS2 spectroscopy to compare the evolutionary states of galaxies in two similar-mass galaxy clusters at z = 0.84 and z = 1.24, divided into samples matched by stellar mass and local dark matter density with similar relative completeness. In the former cluster, it has recently been established that there is ongoing morphological evolution among cluster galaxies, especially between the outskirts and the intermediate-density regions. In our full spectroscopic samples, we notice a substantial downsizing effect in star-formation fractions: the star formation fraction among galaxies of low to intermediate stellar mass (less than 7 x 10^10 Msun) is about twice as high in the z = 1.24 cluster than the z = 0.84 cluster. We also find evidence for a possible time- and density-dependent "settling down" effect among star-forming galaxies. Star-forming galaxies in the intermediate-density regions of the z = 0.84 cluster appear nearly passive with strong D4000, while their z = 1.24 counterparts spectroscopically resemble typical star-forming galaxies with young stellar populations in the outskirts.

ABSTRACT:: I will present an infrared study of a z=0.872 cluster, SpARCS J161314+564930, which distinguished the dynamical histories of spectroscopically confirmed star-forming members to assess the role of cluster environment. Utilizing deep MIPS imaging and a mass-limited sample of 85 spectroscopic members, we identified 16 24um-bright sources within the cluster, and measured their 24um star formation rates (SFRs) down to 6 solar masses/yr. Based on their line-of-sight velocities and stellar ages, MIPS cluster members appear to be an infalling population that was recently accreted from the field with minimal environmental dependency on their star formation. However, we also identified a double-sequenced distribution of star-forming galaxies amongst the members, with one branch exhibiting declining specific SFRs with mass. The members along this sub-main sequence contain spectral features suggestive of passive galaxies. Using caustic diagrams, we kinematically identified these galaxies as a virialized and/or backsplash population. Moreover, we found a mix of dynamical histories at all projected radii, indicating that standard definitions of environment (i.e., radius and density) are contaminated with recently accreted interlopers, which could contribute to a lack of environmental trends for star-forming galaxies. A cleaner narrative of their dynamical past begins to unfold when using a proxy for accretion histories through profiles of constant (r/r_200)*(v/sigma_v); galaxies accreted at earlier times possess lower values of (r/r_200)*(v/sigma_v) with minimal contamination from the distinct infalling population. Therefore, adopting a time-averaged definition for density (as traced by accretion histories) rather than an instantaneous density yields a depressed specific SFR within the dynamical cluster core. These results have been accepted for publication in ApJ.

ABSTRACT:: Mass measurements are of paramount importance in the study of galaxy clusters. When obtaining dynamical cluster masses via velocity dispersion measurements, brighter cluster galaxies may introduce systematic bias. In this talk I will outline the impact of member galaxy selection on velocity dispersion estimates evident in both simulated and observational data sets. We show that there is a systematic underestimation of cluster masses when using the brighter cluster members, an indication that dynamical friction is a serious source of bias when using galaxy velocities as tracers of the underlying potential. We make a recommendation that, in the case of limited spectral fibres, fainter member galaxies be prioritised over the brighter galaxies for a more accurate cluster mass reconstruction.

ABSTRACT:: The IDILICO project is an international collaboration aimed at studying the assembly of galaxy aggregations from high-resolution numerical simulations in the framework of the Lambda-CDM concordance cosmology. We recently finished the construction of a realistic set of N-body models of pre-virialized galaxy groups, specifically tailored for the understanding of the role of gravity on structure formation and galaxy evolution. Here we present results on the evolution of 1) The fraction of intragroup light (IGL). 2) The merging rate and the spiral galaxy fraction. 3) The visible component luminosity function. The approach used in this work relies on standard astronomical tools such as sextractor and galfit applied to 2D projections and their comparison to model values. A diffuse IGL appears as a result of the merger process staying gravitationally bound to the visible group at any time.

ABSTRACT:: We present our study on a large-scale filamentary structure in the COSMOS field. This structure is located within an extremely narrow redshift slice at z~0.73, extends across ~20 Mpc, and encompasses a comprehensive range of environments: from dense cluster cores and galaxy groups to filaments, less dense regions and voids. It provides thus a valuable laboratory for the accurate mapping of environmental effects on galaxy evolution at a lookback time of ~6.5 Gyr. We have obtained new deep spectroscopic observations with VIMOS at VLT and we have build a complete sample of galaxies down to a significantly lower mass limit than that reached with the zCOSMOS data. The spectroscopic information of this statistically robust sample of galaxies permits the detailed mapping of the structure and thus studying galaxy properties as a function of local environment at a redshift where environmental effects have been shown to be important, and in a mass range where mass- and environment-driven effects are both at work.

ABSTRACT:: We present the XXL survey: a 50 deg2 area covered at medium depth with XMM and associated to numerous multi-lambda programmes. The main goal of the project is the first determination of the evolving DE equation of state using galaxy clusters. This is the largest XMM programme to date: http://irfu.cea.fr/xxl The XMM observations have been completed early 2013; source lists and cluster catalogues are processed. An ESO large programme has been allocated to obtain the cluster redshifts. We discuss the impact of critical issues in the cosmological analysis of cluster samples namely: selection functions, scaling relations and the problem of the mass determination of z>1 clusters. We present a new cosmological method based on X-ray colour-magnitude diagrams, which allows one to by-pass the tedious steps of the determination of the cluster mass function. And we illustrate a number of requirements for future numerical simulations to efficiently support such cosmological analyses.

ABSTRACT:: We analyze the potential and optimization of the upcoming X-ray cluster telescope eROSITA to simultaneously constrain cosmological and X-ray scaling-relation parameters via the measurement of the abundances and angular clustering of a photon-count limited sample of clusters up to z~1.5. Special attention is dedicated to the primordial non-Gaussianity alternative and the Dark-Energy models. We discuss our findings taking into account the systematic uncertainties within the adopted underlying theoretical models, we emphasize the impact of the uncertainties in the mass-observable relations onto the cosmological constraints, and systematically compared the cosmological forecasts by two complementary statistical techniques, the Fisher Matrix Formalism and Markov Chain Monte Carlo.

ABSTRACT:: This work is aimed at performing a thorough analysis of the star formation activity in the young massive galaxy cluster RXJ1257+4738 at z=0.866, with emphasis in the relationship between the local environment of the cluster galaxies and their star formation activity. We have performed an optical and infrared study that benefited from the large amount of data available for this cluster, including new OSIRIS/GTC and Herschel imaging observations. Using a comprehensive multi-wavelength catalogue we measured photometric redshifts through a chi2 SED-fitting procedure. We implemented a robust cluster membership selection criterion including Monte Carlo simulations, deriving a sample of 426 reliable cluster member galaxies for which we measured properties as optical colours, stellar masses, ages, UV and IR luminosities, and local densities. From the sample of 426 cluster galaxies, 75 show FIR emission at our detection limits. The spatial distribution of these cluster FIR emitters within the cluster density map and the filament-like overdensities observed, suggest that RXJ1257 is not virialised but in the process of assembly. The average star formation as a function of the cluster environment parametrised by the local density of galaxies does not show any clear trend. However, the fraction of star forming galaxies unveil a different density dependence behaviour for low and high mass galaxies: the fraction of FIR low-mass galaxies decreases towards high density environments, while the fraction of FIR high-mass galaxies increases. We propose ram pressure as a physical mechanism that could explain the quenching of the star formation in low-mass galaxies and possibly a re-triggering in high-mass ones.

ABSTRACT:: We present a new set of cosmological hydrodynamical simulations of galaxy clusters and groups performed with the TreePM+SPH GADGET-3 code. We carried out one set of non-radiative simulations and two sets of simulations including radiative cooling, star formation, metal enrichment and feedback from supernovae (SNe), one of which also accounting for the effect of feedback from AGN. We present the general analysis of this set of cosmological simulations with the aim of studying the relative role played by the different feedback schemes on the main properties of our sample of galaxy clusters: their X-ray scaling relations, their baryon content and its implication in constraining cosmological parameters, and the production and distribution of metals within clusters. Our results are compared with results obtained from recent observational samples. With respect to previous similar analysis, the simulations used in this study provide us with a sufficient statistics of massive objects and including an efficient AGN feedback.

ABSTRACT: One key scientific objective of the CLASH program is to measure the matter concentration, c, as a function of cluster mass for an x-ray selected sample of clusters. We have observed 20 x-ray selected clusters in CLASH, selected with the following attributes: Tx ≥ 5 keV, low x-ray surface brightness eccentricity, and limited or no x-ray substructure. The motivation for this selection was to minimize lensing-selection effects that can potentially bias the concentration to higher values for a given Virial mass. I will present preliminary results, derived using the SaWLENS algorithm, on the c-M relation for the x-ray selected clusters in CLASH and will show these results compare with the expectations from current N-body simulations.

ABSTRACT: The SZ and X-ray signals both trace the gas distribution in galaxy clusters and so can be used to verify some of the key predictions of the theory of structure formation. I will discuss the current state of play in the comparison of X-ray and SZ measurements, and what needs to be done to improve observational constraints.

ABSTRACT: Clusters are Dark Matter (DM) dominated in the outskirts, but in the very central regions baryons play an important role. In particular the Brightest Cluster Galaxy (BCG) corresponds to the spatial range where the trend inverts and stars dominate the total mass. Thus focusing on BCG baryon properties one can asses the mass density profile and the contribution of both stars and DM to the total mass budget. Spatially resolved studies of the stellar kinematics can probe the mass distribution from the innermost scales, i.e. r<5-7 kpc where stars dominate the mass, out to larger radii, i.e. 750-60 kpc, another baryon component usually arises and should be taken into account: the intra-cluster light (ICL). The ICL consists of stars which are now bound to the cluster potential after beeing stripped from member galaxies as they interacted and merged with either the BCG or the other member galaxies. The ICL signature can be seen in the surface brightness (SB) profile of the BCG as an excess of light with respect to the typical r$^{1/4}$ law. Both kind of studies have been performed mainly at low redshifts, i.e. z < 0.3. In this talk I will present the new results obtained for both BCG stellar kinematics and ICL properties in a subset of clusters of the CLASH sample. The CLASH survey comprises 25 massive clusters of galaxies in the redshift range 0.2 < z < 0.8. Among these, 14 have been selected for spectroscopic follow-up at the VLT and photometric follow-up with SUBARU. At completion, both photometric and dymanical properties of each cluster will be available allowing the study of both mass profiles and ICL and its connection to cluster properties/assembly history.

ABSTRACT:: Recent observations have shown that early-type galaxies have undergone a significant size growth between z~1-3 and today. The physical processes responsible for the size evolution (e.g. major mergers, dry minor mergers, AGN feedback) are still in debate. We will present results comparing the mass-size relation for early-type galaxies at those critical redshifts (1.2

ABSTRACT:: The angular power spectrum of the thermal Sunyaev-Zel'dovich (tSZ) effect is an effective tool for constraining cosmology due to its sensitivity on key cosmological parameters like the normalization of the matter power spectrum. Conversely, if the relevant cosmological parameters are known from other experiments, the tSZ power can be used to probe the gas distribution inside galaxy groups and clusters out to the redshift of their formation. In our work we explore the latter path to limit the extent of non self-similar evolution in some cluster scaling relations. Using SPT measured values of the CMB bandpowers we are able to test non-standard scenarios like a redshift dependent gas-mass fraction or a changing ratio of cool core to non-cool core clusters. We use simulated bandpowers for the upcoming CCAT experiment to show how its improved sensitivity and better angular resolution can help to constrain the evolution of the gas mass fraction to better than 10% accuracy.

ABSTRACT:: In 2012 we have performed DEUS Full Universe Runs (Alimi et al 2012), the first simulations of structuration of the entire observable universe and largest to date. These simulations have evolved 550 billion particles and 2 trillion AMR cells down to z=0 for 3 dark energy models. They follow the formation of 150 million galaxy clusters and allow to build for the first time full-sky lightcones with ALL the galaxy clusters between z=0 and 3. I would like to present first results about the most massive clusters in the universe, their large scale distribution as well as non universal mass functions. On the other hand within BINGO! Consortium, we have performed hydrodynamical simulations featuring 3 scenarios of feedback including AGN jet feedback. I will highlight some key results about how it affects the distribution of baryons. These 2 simulation suite could serve as a good basis to perform a campaign of full physics zoom-simulation onto the most massive clusters of the universe.

ABSTRACT:: Precision cosmological surveys aim to constrain the nature of dark energy and dark matter. In particular, the evolution of the abundance of galaxy clusters depends upon the properties of dark energy via the growth rate of cosmic structure. Accurate numerical simulations are needed to compare observations with theory. Percent level accuracy in cluster properties, while achievable (but far from trivial) for gravity-only (dark matter) simulations, is a difficult challenge once baryon physics and mass-observable relations are included. I discuss some of the recent progress toward accurate cosmological simulations, with a focus on gravity-only runs. I also discuss some of the remaining challenges that must be overcome to utilize fully the cluster mass function in cosmological surveys.

ABSTRACT:: In this contribution we will give a complementary view of the large-scale matter distribution focusing on the most underdense regions of the Universe, the so-called voids. Cosmic voids represent one of the most prominent feature of the cosmic web. They occupy most of the volume of the Universe and are believed to play an essential role in the organization of the cosmic matter distribution. We will present the results of an Eulerian adaptive mesh refinement (AMR) hydrodynamical and N-body simulation that has been specifically designed to follow the formation and evolution of voids. To analyse the outcome of this simulation, we have constructed a void finder optimally suited to find the hierarchy of voids in AMR simulations. In a cosmological box of comoving side length 100 Mpc/h we identify hundreds of voids with sizes up to 17 Mpc/h, which show a complex morphology and an intricate hierarchy of nested structures. The analysis of their mass density profiles leads to the conclusion that a universal density profile can be applied to voids of any size, density, morphology and redshift.

ABSTRACT:: Using data from the Scientific Verification phase of the Dark Energy Survey, we will present results derived from deep, multi-colour, images of XMM clusters made using the DECam instrument. Some of these clusters are well known (e.g. The Bullet Cluster), but many of these clusters have been confirmed for the first time using DECam data. DECam images and preliminary optical to X-ray scaling relations, will be shown. We will also: Give a brief overview of DECam, DES-SV and of the Dark Energy Survey. Describe the methods used to generate XMM images of more than 100 clusters that overlap with the DES-SV region (these methods have been adapted from those used in the XMM Cluster Survey, XCS). And, finally, preview a complete catalogue of extended XMM sources (with an integrated selection function) that is soon to be released by XCS.

ABSTRACT:: The survey of galaxy clusters performed by Planck through the Sunyaev-Zeldovich effect has already discovered many interesting objects, thanks to the whole coverage of the sky. One of the SZ candidates detected in the early months of the mission near to the signal to noise threshold, PLCKG214.6+37.0, was later revealed by XMM-Newton to be a triple system of galaxy clusters. I will present results from a deep XMM-Newton re-observation. The characterisation of the physical properties of the three components has allowed us to build a template model to extract the total SZ signal of this system with Planck data, allowing us to partly reconcile the discrepancy between the expected SZ signal from X-rays and the observed one. The analysis of the dynamical state of the three components, as well as the absence of detectable excess X-ray emission, suggest that we are witnessing the formation of a massive cluster at an early phase of interaction. Moreover, I will also report on the detection by Planck (the first with SZ) of hot diffuse intercluster gas between pairs of merging clusters

ABSTRACT:: I will present the evolution in the luminosity function (LF) of passive cluster galaxies over the last 10 billion years. Our observations probe well down the faint red sequence LF in clusters at z deficit of faint galaxies compared to its likely descendant clusters at z0.7.

ABSTRACT:: We present new far-infrared (FIR) imaging data of the proto-cluster region around the radio-galaxy PKS 1138-262 at z = 2.2 (the so-called Spiderweb galaxy), obtained with the PACS and SPIRE instruments on-board the Herschel Space Observatory (HSO). The acquired photometric maps of ~ 10 x 10 arcmin at 100 and 160 micron and ~ 30x30 arcmin at 250, 350 and 500 micron, centred on the radio-galaxy, were used to produce band-merged multi-wavelength catalogue, supplemented with publicly available mid-infrared photometric data from Spitzer. Best match spectral energy distributions (SEDs) with Herschel templates are derived for all sources that are detected at high signal-to-noise ratio, including 4 spectroscopically confirmed members. Based on the SED and the overall FIR spectral shape we identify a sample of candidate proto-cluster members. The SEDs are then used to derive the total FIR luminosities, star formation rates and dust masses. The very high star formation rates observed (~500 to ~1000 Msun/yr) are consistent with those derived from mid-IR spectroscopy. The Halpha - derived SFRs are much smaller than the values quoted above, suggesting a highly obscured SF activity.To quantify statistically the overdensity of the IR galaxies associated with the Spiderweb proto-cluster, we calculate the source counts in both PACS and SPIRE and the two-point angular correlation function (2p-ACF).

ABSTRACT:: Star-formation in the galaxy populations of local massive clusters is known to be less pronounced with respect to field galaxies, and also tends to be suppressed in the core region. Using deep imaging in the range 100-500mum from Herschel, we investigate the far-infrared properties of the cluster members of XMMU J2235.3-2557, one of the most massive, distant clusters known to date. The luminosity derived star formation rate (SFR) of 16 galaxies individually detected by Herschel ranges from 89-463 Msun/yr. This sample of cluster galaxies is located beyond the core region. The stacking analysis of 9 star-forming members that are not detected by Herschel allows us to reach the main-sequence level. Using a colour criterion we select 41 PACS sources as candidate star-forming cluster members. In this study we characterize a population of highly obscured SF galaxies in the outskirts of XMMU J2235.3-2557. We do not find evidence for a reversal of the SF-density in this distant cluster.

ABSTRACT:: We present constraints on cosmological parameters as obtained from X-ray selected galaxy cluster samples (the Vikhlinin et al. 2009 and RDCS samples). Through this analysis we show the importance of the contribution of high-redshift clusters when we want to constrain the DE EoS. We present results obtained from a low-redshift statistically larger optical cluster catalogue (the maxBCG sample) underlying the importance of the power spectrum contribution to cosmological parameter constraints. Given the importance of having a high redshift statistically large catalogue of galaxy clusters, we provide forecasts for a survey with both these characteristics. Thus we perform a forecast analysis for the Euclid photometric cluster survey with the MCMC method. In particular we focus on constraints obtained for the neutrino mass and effective number of neutrino species. Finally, given the importance of the clustering of clusters and knowing that the density fluctuation calculated in a given Friedmann background is not gauge invariant, we compute a gauge invariant expression for the angular correlation function which can be straightforward compared with observations, following the approach provided by Bonvin & Durrer 2011.

ABSTRACT:: A short review of ongoing work and status of the core program of the future Euclid mission.

ABSTRACT:: One of the challenges of future precision cosmology missions is to fully understand and characterize the effects of baryons on the formation of structures and the bias between dark matter and baryonic matter distributions. We use the EAGLE hydrodynamical simulation suite to study the matter density profiles of haloes up to 10^14 solar masses. These simulations provide a unique virtual catalogue of galaxies, matching the observed current Universe, at an unprecedented resolution. Matching the observed mass function of galaxies requires effective feedback from supernovae and black holes. These result in strong outflows of baryons from their host dark matter haloes. In this talk, I will present the shape of these simulated matter profiles for different halo sizes across all redshifts and analyse the different contributions to the halo mass. I will also discuss the differences with pure DM results and their implications for future cosmology surveys.

ABSTRACT:: We found that a significant fraction (38%) of red early-type galaxies (Mr (A119, A2670, A3330 and A389, Sheen et al. 2012). We used CTIO 4-m Blanco telescope to achieve mu_r = 30 mag arcsec^-2 images of the clusters. The unusually deep optical images revealed faint post-merger features around the cluster early-type galaxies. Surprisingly, the post-merger fraction is almost comparable to what was found earlier in low-density field environments, 49% (van Dokkum 2005), while the ongoing merger fraction is significantly lower in the clusters. Our result challenges the classical cluster dynamics which claims that galaxies in clusters have large peculiar motions which prevent frequent galaxy mergers. In addition to that, it is expected that galaxy formation and evolution processes took place rapidly at early epoch in cluster environment. We interpreted our result as that the galaxies are carrying their post-merger signatures from their previous dark matter halo in which galaxy mergers could occur easily as it does in the field environment. The apparent lack of dependence of the merger fraction on the clustocentric distance was also naturally explained this way. This result suggest that a certain fraction of cluster early-type galaxies are assembled at recent epoch. Also it reminds us of how important it is to trace back the previous halo environment of cluster galaxies to understand them. We will also discuss on their UV-optical properties which may be related with their merger events.

ABSTRACT:: Over the past several years, the comparatively low background of the Suzaku satellite has enabled measurements of the thermodynamic properties of the faint cluster outskirts, opening a new window for the exploration of the ongoing virialization and equilibration processes that occur as part of large-scale structure formation. Due to the low surface brightness of these regions, a detailed understanding of the systematic uncertainties related to both the instrument and sky backgrounds is vital. I will discuss the data analysis procedures and demonstrate the robustness of the thermodynamic measurements near the virial radii in bright, nearby clusters.

ABSTRACT: It is well established that cosmological simulations of galaxy clusters have trouble reproducing the gas-poor, red galaxies that are observed in the centers of real clusters, instead producing conditions that are essentially the exact opposite. Thermal conduction has been theorized to help mitigate this problem by transporting heat from the hot intracluster medium (ICM) to the dense, cooling gas in the core. We present the results of a series of cosmological simulations of ten clusters performed with isotropic conduction and with five values for the conduction suppression factor. We find that for conduction suppression factors higher than 0.1, conduction is able to create a roughly isothermal core. More surprisingly, we also find that conduction systematically decreases the gas density and temperature near the virial radius. We show that this is due to alteration of the accretion shocks by the process of conduction itself. These findings may offer new possibilities for observing conduction in galaxy clusters.

ABSTRACT:: Cl J1449+0856 at z=2 is the most distant galaxy cluster for which an extended X-ray emission has been detected. With an estimated mass of a typical today's massive cluster progenitor, it allows the study of galaxy populations in most dense environments 10 billion years ago, a crucial time bridging proto-clusters to the first established clusters, and marking the main formation epoch of massive cluster galaxies. In the core of this system, a remarkably diverse galaxy population clearly shows how galaxy evolution is in a much more active phase as compared to cluster cores at z<1-1.5. Nonetheless, together with still actively forming galaxies, we identify a population of massive passive sources with an early-type morphology. Although smaller than similarly massive early-types in the nearby Universe,they seem generally larger than their z~2 field counterparts, possibly supporting recent claims of an accelerated structural evolution of early-types in high-redshift dense environments.

ABSTRACT:: Massive clusters of galaxies formed from vast cosmological volumes and are believed to be representative of the baryon budget of the Universe. It is therefore interesting to investigate the variation of the baryon fraction with cluster mass and its evolution with redshift. We measure baryon fractions for a unique sample of 14 very massive, high-redshift clusters (median redshift 0.93, median mass 5 x 10^14 Msol) detected via their Sunyaev-Zel'dovich signature by the South Pole Telescope. The stellar masses are determined by SED fitting using VLT, HST and SPITZER data. The second component of the clusters' baryonic budget -the gas mass fraction- is measured from the X-ray surface brightness profiles from an extensive Chandra and XMM-Newton programs. We will discuss the stellar and cold baryon fractions as well as the derived baryon fraction in the light of the its cosmological value from the CMB measurements and in comparison with lower mass/redshift samples to constrain its evolution.

ABSTRACT:: The hot, X-ray emitting gas, as the dominant baryon component in groups and clusters, accounts for almost all gas in the intracluster space. However, there are places where multiphase gas components exist, providing important constraints on microtransport processes, star formation, intracluster magnetic field, ionization and heating mechanisms. We summarize our work on the studies of the multiphase medium and star formation in two kinds of unique environment, the stripped tails of cluster galaxies and the group cool cores. The stripped galactic gas has been detected in X-rays, Halpha, MIR H_2, CO and FIR dust. There is also mounting evidence of star formation in the stripped galactic gas by ram pressure and such a mode of star formation may be common in clusters. The initial results of our Halpha narrow-band imaging survey of nearby group cool cores are also presented, along with the multi-wavelength data on several group cool cores from Chandra, HST, EVLA, GMRT and other telescopes.

ABSTRACT:: X-ray studies of velocity structures of the intracluster medium is one of the primary goals for future X-ray missions. High resolution spectroscopy will provide measurements of energy distributions not only in thermal but also in kinematic forms. These provide not only to understanding of cluster formation but also reductions of systematic uncertainties in cluster total masses for precise cosmology. Using Suzaku we have detected a motion of a sub component with a velocity of about 1500 km/s for the first time by X-ray of a X-ray bright merging cluster, Abell2256 (Tamura et al. 2011). We also searched for gas bulk motions in relaxed clusters such as the Perseus. In addition we attempted to measure 'X-ray gas redshift' of clusters. We found that gas are moving in pair with galaxies at least in X-ray bright central regions. Studies of gas bulk motion along with turbulent motions will be drastically advanced by X-ray micro calorimeter onboard ASTRO-H to be launched in 2015.

ABSTRACT: SWift X-ray Cluster Survey (SWXCS) is an ongoing project aimed at finding serendipitous galaxy clusters in the Swift XRT archive. Based on the GRB follow-up fields, we presented a first catalog containing 72 cluster candidates. The catalog is complete, with a well defined selection function and an expected negligible contamination. The X-ray spectra of this catalog were analyzed in detail. A majority of them have their ICM properties characterized with redshift. In order to extend the survey to larger sky coverage and higher sensitivity, we developed a new extended-source detection software "EXSdetect", and performed it on the whole Swift XRT archive. It gave rise to a larger, complete catalog of cluster candidates.

ABSTRACT:: We investigate the evolution of Brightest Cluster Galaxies (BCGs) from redshift z~1.6 to z=0, focusing on their star formation history, to understand the nature of passive evolution in a hierarchical universe, and to produce more solid constraints for AGN feedback recipes. We use the hierarchical semi-analytic model of Croton et al. (2006), upgraded with a new spectro-photometric model that produces realistic galaxy spectra, making use of the Maraston (2005) stellar populations and a new recipe for the dust extinction. We compare the model predictions of the K-band luminosity evolution and the J-K, V-I and I-K colour evolution with a series of datasets, including Collins et al. (Nature, 2009) who argued that semi-analytic models based on the Millennium simulation cannot reproduce the red colours and high luminosity of BCGs at z>1. We show instead that the model is well in range of the observed luminosity and correctly reproduces the colour evolution of BCGs in the whole redshift range up to z~1.6. An analysis of the model BCGs shows an increase in mass by a factor 2-3 since z~1, and star formation activity down to low redshifts. While the consensus regarding BCGs is that they are passively evolving, we argue that this conclusion is affected by the degeneracy between star formation history and stellar population models used in SED-fitting, and by the inefficacy of toy-models of passive evolution to capture the complexity of real galaxies, expecially those with rich merger histories like BCGs. Following this argument, we also show that in the semi-analytic model the BCGs show a realistic mix of stellar populations, and that these stellar populations are mostly old. In addition, the age-redshift relation of the model BCGs follows that of the universe, meaning that given their merger history and star formation history, the ageing of BCGs is always dominated by the ageing of their stellar populations. In a LCDM universe, we define such evolution as 'passive in the hierarchical sense'.

ABSTRACT:: I present recent ALMA, Hubble , and Chandra results that advance our understanding of AGN heating and intracluster medium cooling in the central giant ellipticals of cool core galaxy clusters. Stunning new HST FUV continuum imaging reveals star formation on 30 kpc scales in clumpy, filamentary, and disk-like distributions, many of which exhibit strong evidence for both jet-triggered star formation as well as spatially structured residual cooling channels stemming from the ambient hot X-ray atmosphere. Highlights from recent Chandra results include three unique signatures of mechanical (radio-mode) AGN feedback, including what may be the first direct observational evidence in support of buoyant X-ray cavity heating models invoked to inhibit cooling flows at late epochs. Finally, I discuss exciting recent and forthcoming ALMA observations of the morphologically and kinematically complex cold gas reservoirs in cool core brightest cluster galaxies. Cool core clusters are thought to harbor the only observable, low-redshift analogues of cooling processes thought to drive galaxy growth at early epochs. The results I present here are therefore relevant not only for cool core physics, but for the baryon cycle in galaxy evolution as a whole.

ABSTRACT:: Merging and interactions are thought to be major drivers of galaxy evolution. SWXCS is a new, X-ray detected cluster sample constructed making use of the archive of the XRT, the X-ray telescope on board of the Swift satellite. We describe the survey, its X--ray properties, and the optical counterpart catalog. The wide dynamic range of masses of the SWXCS survey of groups and clusters offers an ideal opportunity to test some of our key ideas on how the local environments affect the galaxy transformation, e.g. the evolution of the mass-size relation.

ABSTRACT:: We measure the stellar mass functions (SMFs) and the radial stellar mass profiles of 10 rich clusters in the Gemini Cluster Astrophysics Spectroscopic Survey (GCLASS) in the redshift range 0.86 ents at similar redshifts from the COSMOS/UltraVISTA survey, and distinguish between star-forming and quiescent galaxies. We find that for each galaxy type the best-fitting Schechter parameters alpha and M^* are similar for the different environments. The difference in the shape of the total SMF between the clusters and the field is therefore due to a higher fraction of quiescent galaxies in clusters. This poses a challenge to analytical models that attempt to explain the build-up of the quiescent population by a combination of mass-, and environmental quenching.

ABSTRACT:: I will present my result of the theoretical characterization of the sources of non-thermal energy (turbulence, magnetic fields, cosmic rays) in the intra-cluster medium, using high-resolution simulations and new developments in the grid code ENZO. A comparison with available X-ray, gamma and Radio data will be discussed in detail.

ABSTRACT:: Strong lensing is one of the most direct probes of both the mass distribution in galaxy clusters and of the cosmological abundance of clusters. Indeed, not only lensing is used to constrain the density profiles and the masses of clusters, but the distribution of (large) Einstein radii depends on the cosmological distribution function of masses of clusters. We make comprehensive predictions of the Einstein radius distribution function through a combination of numerical methods based on detailed ray-tracing in state-of-the-art MUSIC simulated clusters and a semi-analytical method to infer the evolution with redshift of the distribution. The variance in the predictions arises from a number of reasons: the presence of sub-structures, orientation, concentration, unrelaxed configurations, which are difficult to assess analytically and can only be studied through massive Monte Carlo simulations.

ABSTRACT:: We use Spitzer 3.6um and 4.5um imaging supplemented with ground based optical/NIR data to study the galaxy populations in distant (0.81e14 Msun. We constrain the assembly epoch of assembly of the cluster population by comparing the evolution of the luminosity function and colors of cluster galaxies to stellar population synthesis models. The relation between the two main baryonic component (hot gas and stars) is studied via comparison of X-ray observables and optical ones, including total stellar mass, luminosity and density profiles.

ABSTRACT:: I will present new constraints on dark matter coldness by using the high redshift Lyman-alpha forest.

ABSTRACT:: In general, galaxies have experienced different environments during their lifetimes. For instance, a galaxy that currently resides in a massive cluster could have been accreted from a region of the Universe with “average” density, or as part of a galaxy group where it could have spent a significant amount of its life. Within this context, it is extremely important to understand the specific roles that different environments play on galaxy evolution, disentangling them from those of “internal” galactic processes. In this contribution, I will present the results of numerical simulations aimed to study the influence of the environment in the evolution of galaxies, probing different orbital, structural and kinematical properties of galaxies. Specifically, I will describe the role associated to the global tidal field of groups, as well as that linked to close-encounters between galaxies. I will also show preliminary results on the evolution of the gaseous components of groups and galaxies.

ABSTRACT:: Cluster of galaxies have an excellent track record as probes of cosmology. However, if they are to remain competitive with other methods for constraining cosmological parameters, we will need to calibrate the relationships between cluster masses and the observable quantities used to trace mass to better than a few percent accuracy. If we are to succeed in that effort, we will need standard definitions for cluster observables and cluster masses, so that our efforts at percent-level calibration and comparisons with simulations do not become bogged down in sorting out subtle differences among those definitions. Many of the standard observables currently used in cluster cosmology are linked to the highly successful halo model of structure formation, but standards based on purely observational signals may also play an important role as comparisons between observations and models move into the realm of synthetic skies.

ABSTRACT:: Distinguishing the separate contributions of environmental versus in situ processes is critical to understanding galaxy evolution. Observational studies have had increasing success quantifying separately the role of environment and mass in shaping galaxy properties.But it is yet not clear how they are related. I will show that surprisingly the observed mass function (MF) is very similar in the field, groups and clusters and its evolution with time(from z=0.6 to 0)does not depend on environment.To shed light on the processes that drive the MFs,I make use of mock observations of semi-analytic models to carefully compare with observations at different halo masses and redshift.Tuned to match the field MF at z=0,current models struggle to reproduce the MF of clusters at low z and tend to over-predict the number of low mass galaxies in both clusters and field at z~0.6.The nature of these discrepancies provide valuable insight into the processes regulating mass growth in the real universe.

ABSTRACT:: We present the results of an infrared (IR) study of high-redshift galaxy clusters with the MIPS camera on board the Spitzer Space Telescope. We have assembled a sample of 42 clusters from the Red-Sequence Cluster Survey-1 over the redshift range 0.3 t cluster mass and find it increases to higher redshift. Fitting a simple power-law we measure evolution of (1+z)^{5.1\pm1.9} over the range 0.3 e contribution to the mid-IR galaxy emission, will alter the overall number counts per cluster and their rate of evolution. Under the star formation assumption we infer the approximate total SFR per unit cluster mass (~SFR/M_cluster). The evolution is similar, with ~SFR/M_cluster ~(1+z)^{5.4\pm1.9}. We show that this can be accounted for by the evolution of the IR-bright field population over the same redshift range; that is, the evolution can be attributed entirely to the change in the in-falling field galaxy population. We show that the ~SFR/M_cluster (binned over all redshift) decreases with increasing cluster mass with a slope (~SFR/M_cluster ~ M_cluster^{-1.5\pm0.4}) consistent with the dependence of the stellar-to-total mass per unit cluster mass seen locally. The inferred star formation seen here could produce ~5-10% of the total stellar mass in massive clusters at z = 0, but we cannot constrain the descendant population, nor how rapidly the star-formation must shut-down once the galaxies have entered the cluster environment. Finally, we show a clear decrease in the number of IR-bright galaxies per unit optical galaxy in the cluster cores, confirming star formation continues to avoid the highest density regions of the universe at z ~ 0.75 (the average redshift of the high-redshift clusters). While several previous studies appear to show enhanced star formation in high-redshift clusters relative to the field we note that these papers have not accounted for the overall increase in galaxy or dark matter density at the location of clusters. Once this is done, clusters at z~ 0.75 have the same or less star formation per unit mass or galaxy as the field.

ABSTRACT:: I will summarize the highlights from several recently finalized and ongoing Key/Large programs with the Suzaku satellite, targeting the outskirts of the Perseus, Coma, and Virgo clusters, which are the nearest, brightest clusters of galaxies, and are thus ideal targets for studying in detail the physics of the hot X-ray emitting plasma near the virial radii of these systems.

ABSTRACT:: We present a sample of 22 distant (z>0.8) X-ray clusters identified in the 9 deg2 XMM-LSS/CFHT-LS/SWIRE field. Each cluster is identified as an extended X-ray source and is associated with a structure of faint, red galaxies. The sample covers the redshift interval 0.8 1e14 Msolar (though the model dependencies of this number will be discussed). Finally, we will also describe how the 11 deg2 XMM-LSS survey has developed into the 50 deg2 XXL survey and the progress to date in compiling a sample of distant clusters from this ambitious new project.

ABSTRACT:: The diverse evolution history of galaxy clusters can lead to a large scatter of their observable properties at a given mass, which can in turn lead to statistical and systematic errors in cluster mass calibration. To study this scatter, we have developed the Rhapsody simulation - a statistical sample of re-simulated clusters - which allows us to statistically characterize the distribution of and correlation between cluster properties at fixed mass. I will first present the impact of evolution history on the observable properties of galaxy clusters, including the density profiles, galaxy properties and statistics, and velocity dispersions. I will then discuss how we can use this understanding of formation history to optimize the use of cluster mass tracers, to model the covariances between different mass proxies, and to reduce systematic errors in cluster cosmology.

ABSTRACT:: Spitzer has revolutionized studies of distant galaxy clusters. Largely courtesy of IRAC's efficiency at detecting and isolating massive galaxies at high redshift, several dozen clusters have now been confirmed at z>1, including a few massive systems at z>1.5. These cluster samples have, for example, probed the star-formation and mass assembly history of massive galaxies, studied the evolutionary role of AGN in galaxy clusters, and provided a target-rich sample of distant, massive galaxies in which to identify cosmologically interesting Type- Ia supernovae. Most of the distant clusters identified to date come from field surveys, effectively limiting the redshift and mass range of identified structures. Complementary targeted searches for clusters and proto-clusters around radio galaxies have proven quite successful due to the known tendency for radio-loud AGN to reside in rich environments. Taking advantage of this as well as the efficiency with which Spitzer detects and isolates L* galaxies at high redshift, we have identified a large sample of mid-infrared-selected galaxy cluster candidates from ~ 400 powerful radio-loud AGN fields observed by our 400 hr Warm Spitzer program, `Clusters around Radio-Loud AGN' (CARLA, Wylezalek et al., 2013). CARLA allows for the first time allows to systematically study the fields of a large sample of powerful radio-loud sources over a wide redshift range. We first isolate high redshift galaxies using IRAC colors and then search for potential overdensities of the IRAC-selected sources around the targeted AGN. Spectroscopic confirmation of the densest fields at z > 1.4 is under way and we will present the first results. Having at least 150 very overdense fields at hand we can also constrain the near-IR luminosity funtion for galaxy clusters at z > 1.3 and measure the evolution of the faint end slope and m*. First results are consistent with passive evolution up to the highest redshifts probed.

ABSTRACT:: The Multidark SImulations of Galaxy Clusters (MUSIC) project has compiled one of the largest samples of high-resolution resimulated clusters-size objects, which have been selected from a large (1Gpc) volume box. The sample comprises more than 1200 clusters and groups, that have been simulated both with radiative and non radiative hydrodynamics. A sub sample of them, ( more than 700 objects) is particularly useful since it constitutes a complete mass limited volume catalogue. From this database of simulated clusters we have studied in detail the calibration, as well as the scatter, in the scaling relations both in SZ (thermal and Kinetic) and X-rays and their evolutions with redshifts up to the pro-cluster scales. We also show that MUSIC cluster present a good agreement with the most recent observed gas fractions quoted in the literature. A clear dependence of the gas fractions with the total cluster mass es also evident in MUSIC.

ABSTRACT:: Fossil galaxy groups (FGs) are extreme systems whose luminosity is dominated by a very massive early-type galaxy. They are supposed to be old structures in which L* galaxies have had enough time to merge and form the giant elliptical, but little is yet know about the distribution and properties of the faintest group members. Indeed, detailed studies only exist for about a dozen FGs. Here we present the optical luminosity functions of a large sample of 34 FGs down to ~ M*+3.5 mag and discuss the implications of our results.

ABSTRACT:: I will review a series of results from our Multi-Epoch Nearby Cluster Survey (MENeaCS), including the discovery and implications of intracluster SNe, the measurement of the SNe rates in this environment, the evolution of faint galaxies, and the incidence rate of tidal features. Connections will be drawn to associated work at intermediate redshifts regarding both the evolution of cluster galaxies and those in the infall regions, and intracluster light.

ABSTRACT:: For a flux-limited sample of ~60 nearby clusters, we calculated the dynamical masses based on the line-of-sight velocity dispersion, and correlated the dynamical masses with the X-ray mass proxies. We carried out a detailed investigation of the dynamical masses with respect to the criteria to obtain them and the properties representing the cluster dynamics. The results indicate that the dynamical mass can be used as a robust mass proxy. And its intrinsic scatter is no more than that of the X-ray luminosity as a mass proxy.

ABSTRACT:: We analyze X-ray surface brightness and emissivity fluctuations in the Perseus cluster observed by Chandra using a power spectrum approach. Truly spectacular statistics accumulated by Chandra on Perseus makes this data set an extremely powerful tool to probe the ICM inhomogeneities below the Poisson level down to per cent level on small scales allowing us to place constraints on a range of ICM microphysics and various mechanisms that drive the inhomogeneities (AGN feedback, ongoing minor mergers and generic ICM turbulence) and observed structures.