Clusters of Galaxies: Setting the Stage |
| |
Authors: | A Diaferio S Schindler K Dolag |
| |
Institution: | 1. Dipartimento di Fisica Generale “Amedeo Avogadro”, Università degli Studi di Torino, Via P. Giuria 1, 10125, Torino, Italy 2. Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Via P. Giuria 1, 10125, Torino, Italy 3. Institut für Astro- und Teilchenphysik der Leopold-Franzens Universit?t Innsbruck, Technikerstrasse 25/8, 6020, Innsbruck, Austria 4. Max-Planck-Institut für Astrophysik, Karl-Schwarzschildstr. 1, P.O. Box 1317, 85741, Garching b. München, Germany
|
| |
Abstract: | Clusters of galaxies are self-gravitating systems of mass ∼1014–1015
h
−1 M⊙ and size ∼1–3h
−1 Mpc. Their mass budget consists of dark matter (∼80%, on average), hot diffuse intracluster plasma (≲20%) and a small fraction
of stars, dust, and cold gas, mostly locked in galaxies. In most clusters, scaling relations between their properties, like
mass, galaxy velocity dispersion, X-ray luminosity and temperature, testify that the cluster components are in approximate
dynamical equilibrium within the cluster gravitational potential well. However, spatially inhomogeneous thermal and non-thermal
emission of the intracluster medium (ICM), observed in some clusters in the X-ray and radio bands, and the kinematic and morphological
segregation of galaxies are a signature of non-gravitational processes, ongoing cluster merging and interactions. Both the
fraction of clusters with these features, and the correlation between the dynamical and morphological properties of irregular
clusters and the surrounding large-scale structure increase with redshift.
In the current bottom-up scenario for the formation of cosmic structure, where tiny fluctuations of the otherwise homogeneous
primordial density field are amplified by gravity, clusters are the most massive nodes of the filamentary large-scale structure
of the cosmic web and form by anisotropic and episodic accretion of mass, in agreement with most of the observational evidence.
In this model of the universe dominated by cold dark matter, at the present time most baryons are expected to be in a diffuse
component rather than in stars and galaxies; moreover, ∼50% of this diffuse component has temperature ∼0.01–1 keV and permeates
the filamentary distribution of the dark matter. The temperature of this Warm-Hot Intergalactic Medium (WHIM) increases with
the local density and its search in the outer regions of clusters and lower density regions has been the quest of much recent
observational effort.
Over the last thirty years, an impressive coherent picture of the formation and evolution of cosmic structures has emerged
from the intense interplay between observations, theory and numerical experiments. Future efforts will continue to test whether
this picture keeps being valid, needs corrections or suffers dramatic failures in its predictive power. |
| |
Keywords: | Galaxies: clusters: general Intergalactic medium Cosmology: large-scale structure of Universe |
本文献已被 SpringerLink 等数据库收录! |
|