COSMOLOGY WITH CLUSTERS OF GALAXIES

This paper reviews the current status of measurements of galaxy clustering at high redshifts (z > 0.3). The focus is on the inherent limitations in the observation and interpretation of the ``evolution of clustering''. It is likely that results from the first attempts to characterize galaxy clustering beyond the ``local'' universe have been significantly limited by sample variance, as the difficulty in assembling large samples over large volumes is exacerbated as the observat...

The increasing sensitivity of current experiments, which nowadays routinely measure the thermal SZ effect within galaxy clusters, provide the hope that peculiar velocities of individual clusters of galaxies will be measured rather soon using the kinematic SZ effect. Also next generation of X-ray telescopes with microcalorimeters, promise first detections of the motion of the intra cluster medium (ICM) within clusters. We used a large set of cosmological, hydrodynamical simula...

The evolution of galaxy cluster counts is a powerful probe of several fundamental cosmological parameters. A number of recent studies using this probe have claimed tension with the cosmology preferred by the analysis of the Planck primary CMB data, in the sense that there are fewer clusters observed than predicted based on the primary CMB cosmology. One possible resolution to this problem is systematic errors in the absolute halo mass calibration in cluster studies, which is ...

The large scale structure of the present Universe is determined by the growth of dark matter density fluctuations and by the dynamical action of dark energy and dark matter. While much progress has been made in recent years in constraining the cosmological parameters, and in reconstructing the evolution in the large--scale structure of the dark matter distribution, we still lack an understanding of the evolution of the baryonic component of the Universe. Located at nodes of...

Clusters of galaxies are studied from a theoretical point of view, comparing with observational results whenever possible. The problem is approached both analytically as well as by means of high-resoultion numerical simulations. The dark matter halo, the hot intracluster gas, and the stellar component are investigated separately. Numerical clusters are consistent with a relatively simple scenario, in which these objects form around local maxima of the primordial density field...

The large-scale structure of the Universe formed from initially small perturbations in the cosmic density field, leading to galaxy clusters with up to 10^15 Msun at the present day. Here, we review the formation of structures in the Universe, considering the first primordial galaxies and the most massive galaxy clusters as extreme cases of structure formation where fundamental processes such as gravity, turbulence, cooling and feedback are particularly relevant. The first non...

We present an analysis of the clustering evolution of dark matter in four cold dark matter (CDM) cosmologies. We use a suite of high resolution, 17-million particle, N-body simulations which sample volumes large enough to give clustering statistics with unprecedented accuracy. We investigate both a flat and an open model with Omega_0=0.3, and two models with Omega=1, one with the standard CDM power spectrum and the other with the same power spectrum as the Omega_0=0.3 models....

How much dark matter is there in the universe and where is it located? These are two of the most fundamental questions in cosmology. We use in this paper optical and x-ray mass determinations of galaxies, groups, and clusters of galaxies to suggest that most of the dark matter may reside in very large halos around galaxies, typically extending to ~200 kpc for bright galaxies. We show that the mass-to-light ratio of galaxy systems does not increase significantly with linear sc...

The distributions of peculiar velocities of rich clusters and of groups of galaxies are investigated for different cosmological models and are compared with observations. Four cosmological models are studied: standard ($\Omega=1$) CDM, low-density CDM, HDM ($\Omega=1$), and PBI. We find that rich clusters of galaxies exhibit a Maxwellian distribution of peculiar velocities in all models, as expected from a Gaussian initial density fluctuation field. The cluster 3-D velocity d...

The latest cosmological observables analyses seem to converge to a concordant view of the cosmological model: namely the power law Lambda-CDM. The recent WMAP results comfort this new standard model. Nevertheless, some degeneracy in the CMB physics do not allow one to exclude alternative models. A combined analysis with other cosmological observations is thus needed. An example of such work is shown here, focusing on the abundance of local clusters. The latter is a traditiona...