The ROSAT-ESO Flux Limited X-ray Galaxy Cluster Survey (REFLEX II) I. Newly identified X-ray luminous clusters at z>=0.2

TL;DR

This paper presents the discovery and spectroscopic confirmation of 22 new high-mass galaxy clusters at redshift z>=0.2 from the REFLEX II survey, expanding the catalog for astrophysical and cosmological research.

Contribution

It introduces newly identified X-ray luminous clusters at intermediate redshifts, detailing their detection, confirmation, and physical property analysis within the REFLEX II survey.

Findings

19 new clusters from REFLEX II detected and confirmed

3 additional clusters from REFLEX III below flux limit

Clusters exhibit high mass and intermediate redshift properties

Abstract

We report 19 intermediate redshift clusters newly detected in the ROSAT All-Sky survey that are spectroscopically confirmed. They form a part of 911 objects in the REFLEX II cluster catalogue with a limiting flux of 1.8\times10^12 erg/s/cm2 in the 0.1-2.4 keV ROSAT band at redshift z >= 0.2. In addition we report three clusters from the REFLEX III supplementary catalogue, which contains objects below the REFLEX II flux limit but satisfies the redshift constraint above. These clusters are spectroscopically followed-up by our ESO NTT-EFOSC2 campaigns for the redshift measurement. We describe our observing and data reduction methods. We show how X-ray properties such as spectral hardness ratio and source extent can be used as important diagnostics in selecting galaxy cluster candidates. Physical properties of the clusters are subsequently calculated from the X-ray observations. This sample contains the high mass and intermediate-redshift galaxy clusters for astrophysical and cosmological applications.