Sunyaev-Zel’dovich galaxy clusters number counts: consequences of cluster scaling-law evolution

¹ Laboratoire Astrophysique de Toulouse-Tarbes, UMR 5572, Université de Toulouse, 14 rue Edouard Belin, 31400 Toulouse, France
e-mail: pierre.delsart@ast.obs-mip.fr; alain.blanchard@ast.obs-mip.fr
² Instituto de Telecomunicações, Universidade de Aveiro, Campus Universitario de Aveiro, 3810-183 Aveiro, Portugal
e-mail: dbarbosa@av.it.pt

Received: 18 June 2010
Accepted: 6 September 2010

Abstract

Aims. Galaxy cluster surveys based on Sunyaev-Zeldovich effect (SZE) mapping are expected from ongoing experiments. Such surveys are expected to provide a significant amount of information relevant to cosmology from the number counts redshift distribution. We estimate predicted SZE counts and their redshift distribution taking the current cosmological constraints and the X-ray cluster temperature distribution functions into account. Comparison between local and distant cluster temperature distribution functions provides evidence of evolution in the abundance of X-ray clusters that is inconsistent with using standard scaling relations of cluster properties in the framework of the current concordance model. The hypothesis that there is some evolution in the scaling law driven by non-gravitational processes is a natural solution to this problem.

Methods. We performed an MCMC statistical study using COSMOMC and combining current CMB observations from WMAP, the SNIa Hubble diagram, the galaxy power spectrum data from SDSS and X-ray clusters temperature distributions to predict SZE cluster number counts.

Results. Our approach allows a first estimation of expected SZ counts that considers both cosmological constraints as well as data on the temperature distribution function in a consistent way. Models in which SZ gas temperature and X-ray temperature follow the same redshift evolution lead to significantly lower SZE clusters number counts with a distinctive redshift distribution. Ongoing microwave SZE surveys will therefore shed new light on intracluster gas physics and greatly help to identify the role of possible non-gravitational physics in the history of the hot-gas component of x-ray clusters.