The Evolution of X-Ray Clusters of Galaxies

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 ≈ 1, and the evolution of the physical properties of the intra-cluster medium out to z ≈ 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 Ωm ≃ 0.3 and σ8 ≃ 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.

A pan-chromatic view of the galaxy cluster XMMU J1230.3+1339 atz= 0.975

“…Vikhlinin et al 2002;Kotov & Vikhlinin 2005;Maughan et al 2006), other studies extending towards higher redshifts find little or no evolution (e.g. O'Hara et al 2007;Rosati et al 2002), or even negative trends with redshift (Ettori et al 2004). XMMU J1230.3+1339 by itself would be consistent with either of the latter two scenarios.…”

Cosmological Parameters from Galaxy Clusters: An Introduction

“…To break this degeneracy we can use the evolution with redshift. The evolution of the XLF is still debated: there is a hint of evolution at the very bright end, but for the typical L * clusters and less luminous ones, there is no evolution almost up to z ∼ 1 (see discussion in the review by Rosati, Borgani & Norman 2002). In other words, most of the clusters, if we exclude the brightest ones, are already in place at high redshift.…”

“…where µ is the mean molecular weight (µ ∼ 0.6) and m P is the proton mass (see Rosati, Borgani & Norman 2002). Here we let the temperature free to change with the radius.…”

AMR Simulations of the Cosmological Light Cone: SZE Surveys of the Synthetic Universe

“…The number density of galaxy clusters as a function of mass and redshift is strongly dependent on a number of cosmological parameters [1,2]. Cluster survey yields depend on the value of the minimum flux probed as a function of redshift, the growth function of structure, and the redshift evolution of the comoving volume element [3].…”

“…The number density of galaxy clusters as a function of mass and redshift is strongly dependent on a number of cosmological parameters [1,2]. Cluster survey yields depend on the value of the minimum flux probed as a function of redshift, the growth function of structure, and the redshift evolution of the comoving volume element [3].The simulation used to generate the light cones described in this poster is of a 512 Mpc/h comoving volume of the universe, with the following cosmological parameters: (Ω b , Ω CDM , Ω Λ , h, n, σ 8 ) = (0. 04, 0.26, 0.7, 0.7, 1.0, 0.9).…”