Volume 592, August 2016
The XXL Survey: First results
|Number of page(s)||10|
|Published online||15 June 2016|
The XXL Survey
X. K-band luminosity – weak-lensing mass relation for groups and clusters of galaxies⋆
1 School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
2 Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC, V8P 1A1, Canada
3 Institut d’Astrophysique de Paris, CNRS UMR 7095 and UPMC, 98bis, bd Arago, 75014 Paris, France
4 Department of Astronomy, University of Geneva, ch. d’Écogia 16, 1290 Versoix, Switzerland
5 Australian Astronomical Observatory, PO Box 915, North Ryde, NSW 1670, Australia
6 Service d’Astrophysique AIM, CEA Saclay, 91191 Gif-sur-Yvette, France
7 Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
8 INAF, IASF Milano, via Bassini 15, 20133 Milano, Italy
9 Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
10 H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, England
11 Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
Received: 19 June 2015
Accepted: 13 October 2015
Galaxy clusters and groups are important cosmological probes and giant cosmic laboratories for studying galaxy evolution. Much effort has been devoted to understanding how and when baryonic matter cools at the centre of potential wells. However, a clear picture of the efficiency with which baryons are converted into stars is still missing. We present the K-band luminosity–halo mass relation, LK,500−M500,WL, for a subsample of 20 of the 100 brightest clusters in the XXL Survey observed with WIRCam at the Canada-France-Hawaii Telescope (CFHT). For the first time, we have measured this relation via weak-lensing analysis down to M500,WL = 3.5 × 1013 M⊙. This allows us to investigate whether the slope of the LK−M relation is different for groups and clusters, as seen in other works. The clusters in our sample span a wide range in mass, M500,WL = 0.35−12.10 × 1014 M⊙, at 0 < z < 0.6. The K-band luminosity scales as log 10(LK,500/ 1012 L⊙) ∝ βlog 10(M500,WL/ 1014 M⊙) with β = 0.85+0.35-0.27 and an intrinsic scatter of σlnLK|M = 0.37+0.19-0.17. Combining our sample with some clusters in the Local Cluster Substructure Survey (LoCuSS) present in the literature, we obtain a slope of 1.05+0.16-0.14 and an intrinsic scatter of 0.14+0.09-0.07. The flattening in the LK−M seen in previous works is not seen here and might be a result of a bias in the mass measurement due to assumptions on the dynamical state of the systems. We also study the richness-mass relation and find that group-sized halos have more galaxies per unit halo mass than massive clusters. However, the brightest cluster galaxy (BCG) in low-mass systems contributes a greater fraction to the total cluster light than BCGs do in massive clusters; the luminosity gap between the two brightest galaxies is more prominent for group-sized halos. This result is a natural outcome of the hierarchical growth of structures, where massive galaxies form and gain mass within low-mass groups and are ultimately accreted into more massive clusters to become either part of the BCG or one of the brighter galaxies.
Key words: galaxies: clusters: general / galaxies: photometry / gravitational lensing: weak / galaxies: stellar content / X-rays: galaxies: clusters / galaxies: groups: general
The Master Catalogue is available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A2
© ESO, 2016
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