Groups and Clusters of Galaxies: Confronting Theory with Observations

Galaxy groups and clusters are key probes of the large-scale cosmological structure of the universe because, as a population, they are the youngest and most massive gravitationaly bound systems in the universe. Indeed, in the local universe they contain more than a third of the warm-hot diffuse gas and more than 70% of the galaxies. They are therefore excellent laboratories foranswering fundamental open questions on galaxy formation and the global evolution of the cosmic baryons.

The study of galaxy groups and clusters is undergoing a revolution on both observational and computational fronts. The availability of high quality observational data from space-based X-ray, optical, IR and UV observatories, and ground-based optical, radio and Sunyaev-Zel'dovich Effect (SZE) telescopes has motivated concerted efforts to establish large, well-defined dataset of groups and clusters with the full gamut of multi-wavelength coverage, most notably the Canadian Cluster Comparison Project (CCCP), the Local Cluster Substructure Survey (LoCuSS), and Galaxy And Mass Assembly (GAMA) project. These and other programmes are starting to mature, revealing a rich landscape of physical processes. In parallel, computational astrophysicists, aided by dramatic advances in raw computing power, have developed simulation algorithms able to capture correctly the effects of large-scale tidal fields while simultaneously resolving the galaxies within group and cluster halos. 

The potential synergy between the rapidly developing observational and computational studies of galaxy groups and clusters in the next few years is therefore huge. The aim of this workshop is therefore to bring together active researchers involved with the various multi-wavelength surveys and numerical simulations of galaxy groups and clusters to assess the current state of affairs by confronting simulations with multi-wavelength observations.  Key science questions that will be addressed include:

• How realistic are the present generation of numerical simulations of galaxy groups and clusters?

• What is the realm of validity of the involved sub-grid physics?  Does the set of prescriptions that results in a “realistic group” also yield “realistic galaxies” and “realistic clusters”?

• What aspects of the observed group and cluster do the simulations capture well? Where do they fail?

• What multi-wavelength observations can one reasonably/reliably compare to simulations? And what can we learn?

• How can we leverage the multi-wavelength observation, from the radio, SZ sub-mm, through IR, optical and UV to X-rays and gamma rays, to further improve the modeling?

• What observational directions do the numerical simulations suggest?