Cosmology with Clusters

Alain Blanchard
IRAP, Observatoire Midi-Pyrénées

Clusters of galaxies are astrophysical structures for which we have the most comprehensive set of observations. Their different contents, dark matter, baryons, metals, can be monitored and their abundance can be determined as well as their evolution with redshift.

In structure formation theories, clusters arise from linear perturbations growing under gravity, entering the non-linear regime. Self-similarity arguments allow to derive scaling laws relating the observable quantities to the mass. Numerical simulations have established that a physically motivated and analytical approaches to the mass function reproduced quite well results of N-body simulations, allowing to relate closely cosmological models to the observed properties of clusters of galaxies. This renders them as unique tools for cosmology. Non-gravitational processes during their formation and evolution add some complexity affecting their straightforward use for constraining cosmological parameters.

In this course I will present the basic observational properties of clusters of galaxies, the fundamental information on dark matter they allow to infer and the basics of their modelling for their use as a cosmological probe in the precision cosmology area.