Discovery of a massive X-ray luminous galaxy cluster at z=1.579

TL;DR

This paper reports the discovery and confirmation of a massive, X-ray luminous galaxy cluster at redshift 1.579, using X-ray data and optical/NIR follow-up, highlighting its significance among distant clusters.

Contribution

The paper presents the first detection and spectroscopic confirmation of a massive galaxy cluster at z=1.579 in the XMM-Newton archive, expanding knowledge of high-redshift cluster properties.

Findings

Detected as a significant extended X-ray source.

Confirmed at z=1.579 with spectroscopic data.

Identified as a massive cluster with high X-ray luminosity.

Abstract

We report on the discovery of a very distant galaxy cluster serendipitously detected in the archive of the XMM-Newton mission, within the scope of the XMM-Newton Distant Cluster Project (XDCP). XMMUJ0044.0-2033 was detected at a high significance level (5sigma) as a compact, but significantly extended source in the X-ray data, with a soft-band flux f(r<40")=(1.5+-0.3)x10^(-14) erg/s/cm2. Optical/NIR follow-up observations confirmed the presence of an overdensity of red galaxies matching the X-ray emission. The cluster was spectroscopically confirmed to be at z=1.579 using ground-based VLT/FORS2 spectroscopy. The analysis of the I-H colour-magnitude diagram shows a sequence of red galaxies with a colour range [3.7 < I-H < 4.6] within 1' from the cluster X-ray emission peak. However, the three spectroscopic members (all with complex morphology) have significantly bluer colours relative to the observed red-sequence. In addition, two of the three cluster members have [OII] emission, indicative of on-going star formation. Using the spectroscopic redshift we estimated the X-ray bolometric luminosity, Lbol = 5.8x10^44 erg/s, implying a massive galaxy cluster. This places XMMU J0044.0-2033 at the forefront of massive distant clusters, closing the gap between lower redshift systems and recently discovered proto- and low-mass clusters at z >1.6.