RASS-SDSS galaxy cluster survey

Abstract

Aims. We explore the mass-to-light ratio in galaxy clusters and its relation to the cluster mass. Methods. We study the relations among the optical luminosity (L op ), the cluster mass (M 200 ) and the number of cluster galaxies within r 200 (N gal ) in a sample of 217 galaxy clusters with confirmed 3D overdensity. We correct for projection effect, by determining the galaxy surface number density profile in our cluster sample. This is best fitted by a cored King profile in low and intermediate mass systems. The core radius decreases with cluster mass, and, for the highest mass clusters, the profile is better represented by a generalized King profile or a cuspy Navarro, Frenk & White profile. Results. We find a very tight proportionality between L op and N gal , which, in turn, links the cluster mass-to-light ratio to the Halo Occupation Distribution N gal vs. M 200 . After correcting for projection effects, the slope of the L op −M 200 and N gal −M 200 relations is found to be 0.92 ± 0.03, close, but still significantly less than unity. We show that the non-linearity of these relations cannot be explained by variations of the galaxy luminosity distributions and of the galaxy M/L with the cluster mass. Conclusions. We suggest that the nonlinear relation between number of galaxies and cluster mass reflects an underlying nonlinear relation between number of subhaloes and halo mass.

SARCS strong-lensing galaxy groups

“…Such scaling relations, characterized by power laws, have been observed on different mass scales and redshifts (e.g. Lin et al 2003Lin et al , 2004Popesso et al 2005;Brough et al 2006;Becker et al 2007;Johnston et al 2007;Popesso et al 2007;Reyes et al 2008;Mandelbaum et al 2008;Rozo et al 2009;Andreon & Hurn 2010;Foëx et al 2012). Usually, scaling relations are investigated using spherical NFW mass at a given density contrast, e.g.…”

“…In the simplest model of structure formation involving a purely gravitational collapse of dark matter haloes, groups and clusters form a population of self-similar objects with simple relations between their total mass and other physical quantities (Kaiser 1986). Numerous works have explored and tried to fully characterize these links between mass and baryonic observables such as the ICM X-ray luminosity, temperature, pressure, or entropy from X-ray observations (Finoguenov et al 2001;Vikhlinin et al 2002;Ettori et al 2004;Arnaud 2005;Kotov & Vikhlinin 2005;Vikhlinin et al 2006;Hoekstra 2007;Rykoff et al 2008;Pratt et al 2009;Leauthaud et al 2010;Okabe et al 2010;Mahdavi et al 2013), the Compton parameters derived from Sunyaev-Zel'dovich (SZ) observations (McCarthy et al 2003;Morandi et al 2007;Bonamente et al 2008;Marrone et al 2009;Lancaster et al 2011;Planck Collaboration et al 2011c,b), or the galaxy velocity dispersions, richness and optical luminosity from optical observations (Lin et al 2003(Lin et al , 2004Popesso et al 2005Popesso et al , 2007Becker et al 2007;Johnston et al 2007;Reyes et al 2008;Mandelbaum et al 2008;Rozo et al 2009;Andreon & Hurn 2010;Foëx et al 2012). However, many observational results have found discrepancies between the theoretical predictions derived from the gravitationally driven model of structure formation (different slope and normalization, break of self-similarity at low mass, large intrinsic scatter, non-standard redshift evolution), thus revealing the combined influence of various non-gravitational physical processes that affect the properties of groups and clusters (e.g.…”

“…On the other hand, a precise characterization of group and cluster masses provides a unique way to probe relevant mechanisms, such as galaxy harassment, ram pressure stripping, or galaxy starvation/strangulation, which drive the evolution of the galaxy properties (stellar mass, size, star formation rate, spectral/morphological type, etc.) as a function of their local environment, from field galaxies to the core of massive clusters (Smail et al 1998;Balogh et al 1999;Tran et al 2003;Treu et al 2003;Dressler et al 2004;Poggianti 2004;Boselli & Gavazzi 2006;Poggianti et al 2006;Balogh et al 2007;De Lucia et al 2007;Jeltema et al 2007;Popesso et al 2007;Huertas-Company et al 2009;Lubin et al 2009;Stott et al 2009;Wilman et al 2009;Balogh et al 2011b;Carollo et al 2013). It is, therefore, very important to use representative group and cluster samples that cover a wide range in mass and redshift to study and constrain the galaxy and ICM properties along with robust and direct mass estimates of the parent halo.…”

Groups of galaxies in the SDSS Data Release 7

“…Obviously, rich groups of galaxies have to be searched for with different search parameters or other methods (see, e.g. Aguerri et al 2007;Popesso et al 2007) than those employed for poor and medium rich groups.…”

“…However, similar algorithms used to compile these catalogues yielded groups of galaxies with rather different statistical properties. Several authors have presented catalogues of rich clusters of galaxies (Miller et al 2005;Aguerri et al 2007;Popesso et al 2007) using the SDSS data. All these group and cluster catalogues are constructed on the basis of spectroscopic data, using certain Article published by EDP Sciences Page 1 of 11 selection criteria.…”