Hot gas in galaxy clusters: Theory and simulations (Reprinted)

The Sunyaev-Zeldovich Effect (SZE) detectable in galaxy clusters has emerged as a powerful new probe of the low-to-intermediate redshift universe (see articles by Birkin-shaw and Rephaeli in this volume, as well the review by Carlstrom et al. [1]). Within the prevailing theory of cosmological structure formation, galaxy clusters form in rare, massive peaks of the cosmic density field. Because of natural biasing, such regions get a “head start” on structure formation on all scales smaller than the cluster scale. As a consequence, galaxy clusters at the present epoch contain the oldest objects in the universe in an evolutionary sense [2]. This makes galaxy clusters intrinsically interesting as astrophysical objects, worthy of study observationally, theoretically, and computationally.