Chandra X‐Ray Observations of the 0.6 < z < 1.1 Red‐Sequence Cluster Survey Sample

Abstract

We present the results of Chandra observations of 13 optically selected clusters with 0.6 < z < 1.1, discovered via the Red-Sequence Cluster Survey (RCS). All but one are detected at S/N > 3, although three were not observed long enough to support detailed analysis. Surface brightness profiles are fitted to β models. Integrated spectra are extracted within R 2500, and TX and LX information is obtained. We derive gas masses and total masses within R2500 and R500. Cosmologically corrected scaling relations are investigated, and we find the RCS clusters to be consistent with self-similar scaling expectations. However, discrepancies exist between the RCS sample and lower z X-ray-selected samples for relationships involving LX, with the higher z RCS clusters having lower LX for a given TX. In addition, we find that gas mass fractions within R2500 for the high-z RCS sample are lower than expected by a factor of ∼2. This suggests that the central entropy of these high-z objects has been elevated by processes such as preheating, mergers, and/or AGN outbursts, that their gas is still infalling, or that they contain comparatively more baryonic matter in the form of stars. Finally, relationships between red-sequence optical richness (Bgc,red) and X-ray properties are fitted to the data. For systems with measured TX, we find that optical richness correlates with both TX and mass, having a scatter of ∼ 30% with mass for both X-ray-selected and optically selected clusters. However, we also find that X-ray luminosity is not well correlated with richness and that several of our sample members appear to be significantly X-ray faint. © 2008. The American Astronomical Society. All rights reserved.