The XMM-LSS survey: optical assessment and properties of different X-ray selected cluster classes^⋆

¹ LAM, OAMP, Pôle de l’Etoile Site Château-Gombert 38, Rue Frédréric Juliot-Curie, 13388 Marseille Cedex 13, France
e-mail: christophe.adami@oamp.fr
² Laboratoire AIM, CEA/DSM/IRFU/Sap, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
³ Institut d’Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, B5C, 4000 Sart Tilman, Belgium
⁴ ESA, Villafranca del Castillo, Spain
⁵ UPMC Université Paris 06, UMR 7095, Institut d’Astrophysique de Paris, 75014 Paris, France
⁶ CNRS, UMR 7095, Institut d’Astrophysique de Paris, 75014 Paris, France
⁷ Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
⁸ Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
⁹ Department of Physics and Astronomy, University of Victoria, Elliot Building, 3800 Finnerty Road, Victoria, V8V 1A1, BC, Canada
¹⁰ INAF-IASF Milano, via Bassini 15, 20133 Milano, Italy
¹¹ School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
¹² Astronomical Institute, Tohoku University 6-3 Aramaki, Aoba-ku, Sendai 980-8578, Japan
¹³ CEA/DSM/IRFU/SPP, CEA Saclay, 91191 Gif-sur-Yvette, France
¹⁴ CEA/DSM/IRFU/SEDI, CEA Saclay, 91191 Gif-sur-Yvette, France

Received: 9 June 2010
Accepted: 28 October 2010

Abstract

Context. XMM and Chandra opened a new area for the study of clusters of galaxies not only for cluster physics, but also for the detection of faint and distant clusters that were inaccessible with previous missions.

Aims. This article presents 66 spectroscopically confirmed clusters (0.05 ≤ z ≤ 1.5) within an area of 6 deg² enclosed in the XMM-LSS survey. Almost two thirds have been confirmed with dedicated spectroscopy only and 10% have been confirmed with dedicated spectroscopy supplemented by literature redshifts.

Methods. Sub-samples, or classes, of extended-sources are defined in a two-dimensional X-ray parameter space allowing for various degrees of completeness and contamination. We describe the procedure developed to assess the reality of these cluster candidates using the CFHTLS photometric data and spectroscopic information from our own follow-up campaigns.

Results. Most of these objects are low-mass clusters, hence constituting a still poorly studied population. In a second step, we quantify the correlations between the optical properties such as richness or velocity dispersion and the cluster X-ray luminosities. We examine the relation of the clusters to the cosmic web. Finally, we review peculiar compact structures in the surveyed area such as very distant clusters and fossil groups.