The Planck SZ Cluster Catalog: expected X-ray properties

¹ Astrophysics group, Blackett Laboratory, Imperial College, Prince Consort road, London NW7 2AZ, UK
e-mail: a.chamballu@imperial.ac.uk
² Laboratoire AstroParticule & Cosmologie (APC, UMR 7164), Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France
³ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099, USA
⁴ DSM/Irfu/SPP, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France

Received: 19 July 2010
Accepted: 29 May 2012

Abstract

Surveys based on the Sunyaev-Zel’dovich (SZ) effect provide a fresh view of the galaxy cluster population, one that is complementary to X-ray surveys. To better understand the relation between these two kinds of survey, we construct an empirical cluster model using scaling relations constrained by current X-ray and SZ data. We apply our model to predict the X-ray properties of the Planck SZ Cluster Catalog (PCC) and compare them to existing X-ray cluster catalogs. We find that Planck should significantly extend the depth of the previous all-sky cluster survey, performed in the early 1990s by the ROSAT satellite, and should be particularly effective at finding hot, massive clusters (T > 6 keV) out to redshift unity. These are rare objects, and our findings suggest that Planck could increase the observational sample at z > 0.6 by an order of magnitude. This would open the way for detailed studies of massive clusters out to these higher redshifts. Specifically, we find that the majority of newly-detected Planck clusters should have X-ray fluxes 10^-13   erg/s/cm² < f_X [0.5−2   keV]  < 10^-12   erg/s/cm², i.e., distributed over the decade in flux just below the ROSAT All Sky Survey limit. This is sufficiently bright for extensive X-ray follow-up campaigns. Once Planck finds these objects, XMM-Newton and Chandra could measure temperatures to 10% for a sample of  ~100 clusters in the range 0.5 < z < 1, a valuable increase in the number of massive clusters studied over this range.