A z=0.9 supercluster of X-ray luminous, optically-selected, massive galaxy clusters

TL;DR

This paper reports the discovery and detailed analysis of a supercluster at redshift 0.9, composed of three massive galaxy clusters confirmed through X-ray, optical, and lensing observations, representing an early stage of cluster evolution.

Contribution

It presents the first detailed multi-method characterization of a supercluster at z=0.9, combining X-ray, optical, and lensing data to confirm its mass and structure.

Findings

The supercluster contains three clusters with masses around 5x10^14 Msun each.

X-ray and optical mass estimates are consistent, validating scaling relations at high redshift.

The structure is likely a precursor to massive z~0.5 clusters.

Abstract

We report the discovery of a compact supercluster structure at z=0.9. The structure comprises three optically-selected clusters, all of which are detected in X-rays and spectroscopically confirmed to lie at the same redshift. The Chandra X-ray temperatures imply individual masses of ~5x10^14 Msun. The X-ray masses are consistent with those inferred from optical--X-ray scaling relations established at lower redshift. A strongly-lensed z~4 Lyman break galaxy behind one of the clusters allows a strong-lensing mass to be estimated for this cluster, which is in good agreement with the X-ray measurement. Optical spectroscopy of this cluster gives a dynamical mass in good agreement with the other independent mass estimates. The three components of the RCS2319+00 supercluster are separated from their nearest neighbor by a mere <3 Mpc in the plane of the sky and likely <10 Mpc along the line-of-sight, and we interpret this structure as the high-redshift antecedent of massive (~10^15 Msun) z~0.5 clusters such as MS0451.5-0305.