Clusters of galaxies are the largest structures in the Universe. Most of the visible matter is in the form of hot gas permeating the volume of the cluster. The bulk of this gas is in thermal equilibrium in the dark matter-dominated potential. This book discusses all aspects of cluster physics beyond this thermal view. It covers topics such as the warm-hot intergalactic medium outside the clusters, non-thermal radiation components, shocks, equilibration processes and the chemical evolution of these structures. The topics are covered from an observational, theoretical and numerical point of view.
This volume provides a useful reference for astronomers and graduate students, in particular for those who are working in high-energy astrophysics and extra-galactic astronomy.
The existence of soft excess emission originating from clusters of galaxies, de ned as em- sion detected below 1 keV in excess over the usual thermal emission from hot intracluster gas (hereafter the ICM) has been claimed since 1996. Soft excesses are particularly - portant to detect because they may (at least partly) be due to thermal emission from the Warm-Hot Intergalactic Medium, where as much as half of the baryons of the Universe could be. They are therefore of fundamental cosmological importance. Soft excess emission has been observed (and has also given rise to controversy) in a number of clusters, mainly raising the following questions: (1) Do clusters really show a soft excess? (2) If so, from what spatial region(s) of the cluster does the soft excess or- inate? (3) Is this excess emission thermal, originating from warm-hot intergalactic gas (at 6 temperatures of?10 K), or non-thermal, in which case several emission mechanisms have been proposed. Interestingly, some of the non-thermal mechanisms suggested to account for soft excess emission can also explain the hard X-ray emission detected in some clusters, for example by RXTE and BeppoSAX (also see Petrosian et al. 2008—Chap. 10, this issue; Rephaeli et al. 2008—Chap. 5, this issue). Focuses on the warm-hot intergalactic medium and non-thermal aspects of clusters Contains a tutorial review about these topics Takes an approach from observational, theoretical, and numerical modeling points of view
Autor*in
Jelle Kaastra
Themen in »Clusters of Galaxies: Beyond the Thermal View«