The XXL Survey

II. The bright cluster sample: catalogue and luminosity function^⋆,⋆⋆

¹ Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
e-mail: fpacaud@astro.uni-bonn.de
² Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, 85748 Garching bei München, Germany
³ H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK
⁴ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille), UMR 7326, 13388 Marseille, France
⁵ Service d’Astrophysique AIM, CEA/DSM/IRFU/SAp, CEA Saclay, 91191 Gif-sur-Yvette, France
⁶ School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
⁷ Service d’Électronique des Détecteurs et d’Informatique, CEA/DSM/IRFU/SEDI, CEA Saclay, 91191 Gif-sur-Yvette, France
⁸ Department of Astronomy and Space Sciences, Faculty of Science, Istanbul University, 34119 Istanbul, Turkey
⁹ Laboratoire Lagrange, UMR 7293, Université de Nice Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, 06304 Nice, France
¹⁰ European Space Astronomy Centre, ESA, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
¹¹ Department of Astronomy, University of Florida, Gainesville, FL 32611, USA
¹² INAF, IASF Milano, via Bassini 15, 20133 Milano, Italy
¹³ Department of Astronomy, University of Geneva, ch. d’Écogia 16, 1290 Versoix, Switzerland
¹⁴ Departments of Physics and Astronomy, and Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, MI 48109, USA
¹⁵ Astrophysics and Cosmology Research Unit, University of KwaZulu-Natal, 4041 Durban, South Africa
¹⁶ Australian Astronomical Observatory, PO BOX 915, 1670 North Ryde, Australia
¹⁷ Department of Earth and Space Sciences, Onsala Space Observatory, Chalmers University of Technology, 439 92 Onsala, Sweden
¹⁸ INAF–Osservatorio Astronomico di Brera, via Brera 28, 20122 Milano, Italy
¹⁹ Institute for Astronomy & Astrophysics, Space Applications & Remote Sensing, National Observatory of Athens, 15236 Palaia Penteli, Athens, Greece
²⁰ National Center for Supercomputing Applications and Department of Astronomy University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
²¹ Department of Physics and Astronomy, Macquarie University, Sydney NSW 2109, Australia
²² INAF–Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio, 5, 35122 Padova, Italy
²³ European Southern Observatory,Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago de Chile, Chile
²⁴ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
²⁵ Faculty of Physics, Ludwig-Maximilians University, Scheinerstrasse 1, 81679 Munich, Germany
²⁶ Institut de Physique Théorique, CEA/DSM/IPhT and CNRS/URA 2306, 91191 Gif-sur-Yvette Cedex, France
²⁷ Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC, Canada
²⁸ Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK
²⁹ ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
³⁰ Astrophysics Department, Max Planck Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany

Received: 3 July 2015
Accepted: 25 November 2015

Abstract

Context. The XXL Survey is the largest survey carried out by the XMM-Newton satellite and covers a total area of 50 square degrees distributed over two fields. It primarily aims at investigating the large-scale structures of the Universe using the distribution of galaxy clusters and active galactic nuclei as tracers of the matter distribution. The survey will ultimately uncover several hundreds of galaxy clusters out to a redshift of ~2 at a sensitivity of ~10^-14 erg s^-1 cm^-2 in the [0.5–2] keV band.

Aims. This article presents the XXL bright cluster sample, a subsample of 100 galaxy clusters selected from the full XXL catalogue by setting a lower limit of 3 × 10^-14 erg s^-1 cm^-2 on the source flux within a 1′ aperture.

Methods. The selection function was estimated using a mixture of Monte Carlo simulations and analytical recipes that closely reproduce the source selection process. An extensive spectroscopic follow-up provided redshifts for 97 of the 100 clusters. We derived accurate X-ray parameters for all the sources. Scaling relations were self-consistently derived from the same sample in other publications of the series. On this basis, we study the number density, luminosity function, and spatial distribution of the sample.

Results. The bright cluster sample consists of systems with masses between M₅₀₀ = 7 × 10¹³ and 3 × 10¹⁴ M_⊙, mostly located between z = 0.1 and 0.5. The observed sky density of clusters is slightly below the predictions from the WMAP9 model, and significantly below the prediction from the Planck 2015 cosmology. In general, within the current uncertainties of the cluster mass calibration, models with higher values of σ₈ and/or Ω_M appear more difficult to accommodate. We provide tight constraints on the cluster differential luminosity function and find no hint of evolution out to z ~ 1. We also find strong evidence for the presence of large-scale structures in the XXL bright cluster sample and identify five new superclusters.