The X-ray luminous galaxy cluster population at 0.9<z<~1.6 as revealed by the XMM-Newton Distant Cluster Project

TL;DR

This paper presents the largest sample of spectroscopically confirmed high-redshift X-ray luminous galaxy clusters, analyzes their properties, and investigates galaxy evolution and cluster dynamics at z>0.9.

Contribution

It provides a comprehensive sample of 22 high-redshift clusters, calibrates redshift estimation techniques, and offers new insights into cluster and galaxy evolution at z>0.9.

Findings

Median cluster mass around 2×10^14 M⊙

Significant offsets of BCGs from X-ray centers at high z

Evidence of evolving galaxy populations with reduced red sequence

Abstract

We present the largest sample of spectroscopically confirmed X-ray luminous high-redshift galaxy clusters to date comprising 22 systems in the range 0.9<z<\sim1.6 as part of the XMM-Newton Distant Cluster Project (XDCP). All systems were initially selected as extended X-ray sources over 76.1 deg^2 of non-contiguous deep archival XMM-Newton coverage. We test and calibrate the most promising two-band redshift estimation techniques based on the R-z and z-H colors for efficient distant cluster identifications and find a good redshift accuracy performance of the z-H color out to at least z\sim1.5, while the redshift evolution of the R-z color leads to increasingly large uncertainties at z>\sim0.9. We present first details of two newly identified clusters, XDCP J0338.5+0029 at z=0.916 and XDCP J0027.2+1714 at z=0.959, and investigate the Xray properties of SpARCS J003550-431224 at z=1.335, which shows evidence for ongoing major merger activity along the line-of-sight. We provide X-ray properties and luminosity-based total mass estimates for the full sample, which has a median system mass of M200\simeq2\times10^14M\odot. In contrast to local clusters, the z>0.9 systems do mostly not harbor central dominant galaxies coincident with the X-ray centroid position, but rather exhibit significant BCG offsets from the X-ray center with a median value of about 50 kpc in projection and a smaller median luminosity gap to the second-ranked galaxy of \sim0.3mag. We estimate a fraction of cluster-associated NVSS 1.4GHz radio sources of about 30%, preferentially located within 1' from the X-ray center. The galaxy populations in z>\sim1.5 cluster environments show first evidence for drastic changes on the high-mass end of galaxies and signs for a gradual disappearance of a well-defined cluster red-sequence as strong star formation activity is observed in an increasing fraction of massive galaxies down to the densest core regions.