COSMOLOGY WITH CLUSTERS OF GALAXIES

Rich clusters of galaxies are the most massive virialized systems known. Even though they contain only a small fraction of all galaxies, rich clusters provide a powerful tool for the study of galaxy formation, dark matter, large-scale structure, and cosmology. Superclusters, the largest known systems of galaxies, extend to (approx) 100h^{-1} Mpc in size and highlight the large-scale structure of the universe. This large-scale structure reflects initial conditions in the early...

Clusters of galaxies, being dark matter dominated, have long been and still are the ideal cosmological targets to study the nature of dark matter. Constraints on the nature of dark matter comes in particular from the observational determination of the distribution of total and baryonic mass in clusters, by comparison with results from cosmological numerical simulations. I present here past and recent results on this research topic.

The most successful cosmological models to date envision structure formation as a hierarchical process in which gravity is constantly drawing lumps of matter together to form increasingly larger structures. Clusters of galaxies currently sit atop this hierarchy as the largest objects that have had time to collapse under the influence of their own gravity. Thus, their appearance on the cosmic scene is also relatively recent. Two features of clusters make them uniquely useful t...

Various cosmological applications of galaxy clusters are presented. Clusters are used to determine the baryon fraction, dark matter distribution and the matter density of the universe. They also contain a wealth of information about structure formation and evolution on different scales: large-scale structure, cluster formation and also galaxy formation via the interaction of cluster galaxies with the intra-cluster medium. In particular, the X-ray satellites CHANDRA and XMM yi...

Clusters of galaxies, the most massive virialized systems known, provide a powerful tool for studying the structure, the mass density, and the cosmology of our universe. Clusters furnish one of the best estimates of the dynamical mass density parameter on 1 Mpc scale, $\Omega_{dyn}$; the best measure of the baryon density fraction in the universe; an excellent tracer of the large-scale structure of the universe; and, most recently, a powerful tracer of the evolution of struct...

Studies of galaxy clusters have proved crucial in helping to establish the standard model of cosmology, with a universe dominated by dark matter and dark energy. A theoretical basis that describes clusters as massive, multi-component, quasi-equilibrium systems is growing in its capability to interpret multi-wavelength observations of expanding scope and sensitivity. We review current cosmological results, including contributions to fundamental physics, obtained from observati...

By virtue of their high galaxy space densities and their large spatial separations, clusters are efficient and accurate tracers of the large-scale density and velocity fields. Substantial progress has been made over the past decade in the construction of homogeneous, objectively derived cluster catalogs and in characterizing the spatial distribution of clusters. Consequently, the constraints on viable models for the growth of structure have been refined. A review of the statu...

We review several aspects of clusters of galaxies and their application to cosmology. We present first results of numerical simulations of the dynamics of the intra-cluster gas and of different interaction processes between cluster galaxies and the intra-cluster gas. In particular metallicity maps are very useful to determine the importance of the different interaction processes. Also mass determination methods and possible sources for uncertainties in the measurements are sh...

Clusters of galaxies can be used for very different kinds of cosmological tests. I review a few of the methods: determination of cluster masses and dark matter content, metal enrichment and its connection to the origin of the intra-cluster gas, and the dynamical state of clusters. The progress in the different fields expected from observations with the new X-ray satellites XMM and Chandra is pointed out.

We report on work done by the Virgo consortium, an international collaboration set up in order to study the formation and evolution of Large Scale Structure using N-body simulations on the latest generation of parallel supercomputers. We show results of 256^3 particle simulations of the formation of clusters in four Dark Matter models with different cosmological parameters. Normalizing the models such that one obtains the correct abundance of rich clusters yields an interesti...