Scaling Relations for Galaxy Clusters: Properties and Evolution

Abstract

Well-calibrated scaling relations between the observable properties and the total masses of clusters of galaxies are important for understanding the physical processes that give rise to these relations. They are also a critical ingredient for studies that aim to constrain cosmological parameters using galaxy clusters. For this reason much effort has been spent during the last decade to better understand and interpret relations of the properties of the intra-cluster medium. Improved X-ray data have expanded the mass range down to galaxy groups, whereas SZ surveys have openened a new observational window on the intracluster medium. In addition, continued progress in the performance of cosmological simulations has allowed a better understanding of the physical processes and selection effects affecting the observed scaling relations. Here we review the recent literature on various scaling relations, focussing on the latest observational measurements and the progress in our understanding of the deviations from self similarity.

CoMaLit – IV. Evolution and self-similarity of scaling relations with the galaxy cluster mass

“…Numerical simulations (Stanek et al 2010) and theoretical predictions (Giodini et al 2013) agree that the relation between the mass M∆ and any observable quantity O can be summarised by the form…”

“…The intrinsic scatter of the LX-M∆ relation is ∼40 per cent (Giodini et al 2013). It is the largest among the various X-ray scaling relations.…”

“…In the first paper , CoMaLit-I), we evaluated systematic differences in lensing and X-ray masses obtained from independent analyses and we quantified the overall level of bias and intrinsic scatter of these mass proxies. The second paper presented the formalism to calibrate an observable cluster property against the cluster mass and applied the methodology to the Sunyaev-Zel'dovich If gravity is the dominant process, the resulting self-similar model predicts scaling relations in form of scale-free power laws (Kaiser 1986;Giodini et al 2013). Numerical simulations (Stanek et al 2010;Fabjan et al 2011) confirmed these scalings and showed that intrinsic scatters around the median relations approximately follow a log-normal distribution.…”

“…We considered observables connected either to the galaxy distribution, i.e., velocity dispersion of galaxies along the line of sight, σv, or optical richness, λ, or to the intra-cluster medium, i.e., the bolometric X-ray luminosity, LX, or the spherically integrated SZ Compton signal, YSZ. In the self-similar scenario, we expect that for clusters in equilibrium the scalings go like (Giodini et al 2013;Ettori 2015) σv ∝ E 1/3 z M 1/3 ∆ ,…”

“…They result from the main gravitational processes driving the cluster evolution (Kaiser 1986;Giodini et al 2013;Battaglia et al 2012;Ettori 2013). Accurate mass-observable relations are also needed to use the abundance of galaxy clusters to constrain cosmological parameters (Vikhlinin et al 2009;Mantz et al 2010bMantz et al , 2014Rozo et al 2010;Planck Collaboration et al 2014b).…”