Optical & Sunyaev-Zel'dovich Observations of a New Sample of Distant Rich Galaxy Clusters in the ROSAT All Sky Survey

TL;DR

This study identifies and characterizes a large sample of distant, massive galaxy clusters using optical, X-ray, and Sunyaev-Zel'dovich observations, providing data to test cosmological models.

Contribution

It presents a new, extensive sample of high-redshift galaxy clusters with multi-wavelength observations, including Sunyaev-Zel'dovich measurements, to evaluate cosmological consistency.

Findings

Detected Sunyaev-Zel'dovich effect in 11 clusters

No tension found with the $\\Lambda$CDM model

Sample includes some of the richest known clusters

Abstract

Finding a sample of the most massive clusters with redshifts $z>0.6$ can provide an interesting consistency check of the $\Lambda$ cold dark matter ($\Lambda$CDM) model. Here we present results from our search for clusters with $0.6\lesssim z\lesssim1.0$ where the initial candidates were selected by cross-correlating the RASS faint and bright source catalogues with red galaxies from the Sloan Digital Sky Survey DR8. Our survey thus covers $\approx10,000\,\rm{deg^2}$, much larger than previous studies of this kind. Deeper follow-up observations in three bands using the William Herschel Telescope and the Large Binocular Telescope were performed to confirm the candidates, resulting in a sample of 44 clusters for which we present richnesses and red sequence redshifts, as well as spectroscopic redshifts for a subset. At least two of the clusters in our sample are comparable in richness to RCS2-$J$232727.7$-$020437, one of the richest systems discovered to date. We also obtained new observations with the Combined Array for Research in Millimeter Astronomy for a subsample of 21 clusters. For 11 of those we detect the Sunyaev-Zel'dovich effect signature. The Sunyaev-Zel'dovich signal allows us to estimate $M_{200}$ and check for tension with the cosmological standard model. We find no tension between our cluster masses and the $\Lambda$CDM model.