The x-ray luminous galaxy cluster population at 0.9 &lt;<i>z</i>≲ 1.6 as revealed by the XMM-<i>Newton</i>Distant Cluster Project

Abstract

We present the largest sample of spectroscopically confirmed X-ray luminous\nhigh-redshift galaxy clusters to date comprising 22 systems in the range\n0.9&lt;z&lt;\\sim1.6 as part of the XMM-Newton Distant Cluster Project (XDCP). All\nsystems were initially selected as extended X-ray sources over 76.1 deg^2 of\nnon-contiguous deep archival XMM-Newton coverage. We test and calibrate the\nmost promising two-band redshift estimation techniques based on the R-z and z-H\ncolors for efficient distant cluster identifications and find a good redshift\naccuracy performance of the z-H color out to at least z\\sim1.5, while the\nredshift evolution of the R-z color leads to increasingly large uncertainties\nat z&gt;\\sim0.9. We present first details of two newly identified clusters, XDCP\nJ0338.5+0029 at z=0.916 and XDCP J0027.2+1714 at z=0.959, and investigate the\nXray properties of SpARCS J003550-431224 at z=1.335, which shows evidence for\nongoing major merger activity along the line-of-sight. We provide X-ray\nproperties and luminosity-based total mass estimates for the full sample, which\nhas a median system mass of M200\\simeq2\\times10^14M\\odot. In contrast to local\nclusters, the z&gt;0.9 systems do mostly not harbor central dominant galaxies\ncoincident with the X-ray centroid position, but rather exhibit significant BCG\noffsets from the X-ray center with a median value of about 50 kpc in projection\nand a smaller median luminosity gap to the second-ranked galaxy of \\sim0.3mag.\nWe estimate a fraction of cluster-associated NVSS 1.4GHz radio sources of about\n30%, preferentially located within 1' from the X-ray center. The galaxy\npopulations in z&gt;\\sim1.5 cluster environments show first evidence for drastic\nchanges on the high-mass end of galaxies and signs for a gradual disappearance\nof a well-defined cluster red-sequence as strong star formation activity is\nobserved in an increasing fraction of massive galaxies down to the densest core\nregions.\n