The XMM-BCS galaxy cluster survey

I. The X-ray selected cluster catalog from the initial 6 deg²

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr. 1, 85748 Garching, Germany
e-mail: rsuhada@usm.lmu.de
² Department of Physics, Ludwig-Maximilians-Universität, Scheinerstr. 1, 81679 Munich, Germany
³ University of Michigan, Physics Department, 450 Church Street, Ann Arbor, MI 48109-1040, USA
⁴ Excellence Cluster Universe, Boltzmannstr. 2, 85748 Garching, Germany
⁵ University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
⁶ Department of Astronomy, 1002 W. Green Street, Urbana, IL 61801, USA
⁷ Department of Physics & Astronomy, University of Pennsylvania, 209 South 33rd St., Philadelphia, PA 19104, USA
⁸ Department of Physics & Astrophysics, University of North Dakota, Grand Forks, ND 58202, USA
⁹ Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
¹⁰ Fermi National Accelerator Laboratory, PO Box 500, Batavia, IL 60510, USA
¹¹ University of California Observatories & Department of Astronomy, University of California, Santa Cruz, CA 95064, USA
¹² University of Chicago, 5640 South Ellis Avenue, Chicago, IL 6063, USA
¹³ Graduate Institute of Astronomy, National Central University, No. 300 Jonghda Rd, Jhongli City 32001, Taiwan
¹⁴ Laboratoire AIM, IRFU/Service d’Astrophysique – CEA/DSM – CNRS – Université Paris Diderot, Bât. 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France

Received: 8 May 2011
Accepted: 26 October 2011

Abstract

The XMM-Newton-Blanco Cosmology Survey project (XMM-BCS) is a coordinated X-ray, optical and mid-infrared cluster survey in a field also covered by Sunyaev-Zel’dovich effect (SZE) surveys by the South Pole Telescope and the Atacama Cosmology Telescope. The aim of the project is to study the cluster population in a 14 deg² field (center: α ≈ 23:29:18.4, δ ≈  −54:40:33.6). The uniform multi-wavelength coverage will also allow us for the first time to comprehensively compare the selection function of the different cluster detection approaches in a single test field and perform a cross-calibration of cluster scaling relations. In this work, we present a catalog of 46 X-ray selected clusters from the initial 6 deg² survey core. We describe the XMM-BCS source detection pipeline and derive physical properties of the clusters. We provide photometric redshift estimates derived from the BCS imaging data and spectroscopic redshift measurements for a low redshift subset of the clusters. The photometric redshift estimates are found to be unbiased and in good agreement with the spectroscopic values. Our multi-wavelength approach gives us a comprehensive look at the cluster and group population up to redshifts z ≈ 1. The median redshift of the sample is 0.47 and the median mass M₅₀₀ ≈ 1 × 10¹⁴   M_⊙ (~2 keV). From the sample, we derive the cluster log N − log S using an approximation to the survey selection function and find it in good agreement with previous studies. We compare optical mass estimates from the Southern Cosmology Survey available for part of our cluster sample with our estimates derived from the X-ray luminosity. Weak lensing masses available for a subset of the cluster sample are in agreement with our estimates. Optical masses based on cluster richness and total optical luminosity are found to be significantly higher than the X-ray values. The present results illustrate the excellent potential of medium-deep, X-ray surveys to deliver cluster samples for cosmological modelling. Incombination with available multi-wavelength data in optical, near-infrared and SZE, this will allow us to probe the dependence of the selection functions on relevant cluster observables and provide thus an important input for upcoming large-area multi-wavelength cluster surveys.