ARlogo Annu. Rev. Astron. Astrophys. 2002. 40: 539-577
Copyright © 2002 by Annual Reviews. All rights reserved

Reprinted with kind permission from Annual Reviews, 4139 El Camino Way, Palo Alto, California, USA

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The Evolution of X-ray Clusters of Galaxies

Piero Rosati,1,3 Stefano Borgani,2 and Colin Norman3,4

1 European Southern Observatory, D-85748 Garching bei München, Germany;
2 Dipartimento di Astronomia dell'Università di Trieste, via Tiepolo 11, I-34131 Trieste, Italy;
3 Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218;
4 Space Telescope Science Institute, Baltimore, Maryland 21218

Abstract. Considerable progress has been made over the last decade in the study of the evolutionary trends of the population of galaxy clusters in the Universe. In this review we focus on observations in the X-ray band. X-ray surveys with the ROSAT satellite, supplemented by follow-up studies with ASCA and Beppo-SAX, have allowed an assessment of the evolution of the space density of clusters out to z approx 1, and the evolution of the physical properties of the intra-cluster medium out to z approx 0.5. With the advent of Chandra and Newton-XMM, and their unprecedented sensitivity and angular resolution, these studies have been extended beyond redshift unity and have revealed the complexity of the thermodynamical structure of clusters. The properties of the intra-cluster gas are significantly affected by non-gravitational processes including star formation and Active Galactic Nucleus (AGN) activity. Convincing evidence has emerged for modest evolution of both the bulk of the X-ray cluster population and their thermodynamical properties since redshift unity. Such an observational scenario is consistent with hierarchical models of structure formation in a flat low density universe with Omegam appeq 0.3 and sigma8 appeq 0.7 - 0.8 for the normalization of the power spectrum. Basic methodologies for construction of X-ray-selected cluster samples are reviewed and implications of cluster evolution for cosmological models are discussed.

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