Distant galaxy clusters in the XMM Large Scale Structure survey

Abstract

(Abridged) Distant galaxy clusters provide important tests of the growth of\nlarge scale structure in addition to highlighting the process of galaxy\nevolution in a consistently defined environment at large look back time. We\npresent a sample of 22 distant (z>0.8) galaxy clusters and cluster candidates\nselected from the 9 deg2 footprint of the overlapping X-ray Multi Mirror (XMM)\nLarge Scale Structure (LSS), CFHTLS Wide and Spitzer SWIRE surveys. Clusters\nare selected as extended X-ray sources with an accompanying overdensity of\ngalaxies displaying optical to mid-infrared photometry consistent with z>0.8.\nNine clusters have confirmed spectroscopic redshifts in the interval 0.8<z<1.2,\nfour of which are presented here for the first time. A further 11 candidate\nclusters have between 8 and 10 band photometric redshifts in the interval\n0.8<z<2.2, while the remaining two candidates do not have information in\nsufficient wavebands to generate a reliable photometric redshift. All of the\ncandidate clusters reported in this paper are presented for the first time.\nThose confirmed and candidate clusters with available near infrared photometry\ndisplay evidence for a red sequence galaxy population, determined either\nindividually or via a stacking analysis, whose colour is consistent with the\nexpectation of an old, coeval stellar population observed at the cluster\nredshift. We further note that the sample displays a large range of red\nfraction values indicating that the clusters may be at different stages of red\nsequence assembly. We compare the observed X-ray emission to the flux expected\nfrom a suite of model clusters and find that the sample displays an effective\nmass limit M200 ~ 1e14 Msolar with all clusters displaying masses consistent\nwith M200 < 5e14 Msolar. This XMM distant cluster study represents a complete\nsample of X-ray selected z>0.8 clusters.\n