Tracing cosmic evolution with clusters of galaxies
Abstract
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 tracers of cosmic evolution. First, clusters are the biggest things whose masses we can reliably measure because they are the largest objects to have undergone gravitational relaxation and entered into virial equilibrium. Mass measurements of nearby clusters can therefore be used to determine the amount of structure in the universe on scales of 1014 1015 M⊙ , and comparisons of the present-day cluster mass distribution with the mass distribution at earlier times can be used to measure the rate of structure formation, placing important constraints on cosmological models. Second, clusters are essentially “closed boxes” that retain all their gaseous matter, despite the enormous energy input associated with supernovae and active galactic nuclei, because the gravitational potential wells of clusters are so deep. The baryonic component of clusters therefore contains a wealth of information about the processes associated with galaxy formation, including the efficiency with which baryons are converted into stars and the effects of the resulting feedback processes on galaxy formation. This article reviews our theoretical understanding of both the dark-matter component and the baryonic component of clusters, providing a context for interpreting the flood of new cluster observations that are now arriving from the latest generation of x-ray observatories, large optical surveys, and measurements of cluster-induced distortions in the spectrum of the cosmic microwave background.
- Publication:
-
Reviews of Modern Physics
- Pub Date:
- April 2005
- DOI:
- 10.1103/RevModPhys.77.207
- arXiv:
- arXiv:astro-ph/0410173
- Bibcode:
- 2005RvMP...77..207V
- Keywords:
-
- 98.80.Bp;
- 98.65.Cw;
- 98.65.Dx;
- 98.80.Cq;
- 98.80.Es;
- 95.35.+d;
- 97.10.Bt;
- 95.30.Sf;
- 95.30.Cq;
- 97.60.Bw;
- 98.54.Cm;
- 98.62.Js;
- 01.30.Rr;
- 98.70.Vc;
- Origin and formation of the Universe;
- Galaxy clusters;
- Superclusters;
- large-scale structure of the Universe;
- Particle-theory and field-theory models of the early Universe;
- Observational cosmology;
- Dark matter;
- Star formation;
- Relativity and gravitation;
- Elementary particle processes;
- Supernovae;
- Active and peculiar galaxies and related systems;
- Galactic nuclei circumnuclear matter and bulges;
- Surveys and tutorial papers;
- resource letters;
- Background radiations;
- Astrophysics
- E-Print:
- 54 pages, 15 figures, Rev. Mod. Phys. (in press)