CHANDRA X-RAY OBSERVATIONS OF THE 0.6 < z < 1.1 RED-SEQUENCE CLUSTER SURVEY SAMPLE

摘要

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 T_X and L_X information is obtained. We derive gas masses and total masses within R_(2500) and R_(500). 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 L_X, with the higher z RCS clusters having lower L_X for a given T_X. In addition, we find that gas mass fractions within R_(2500) 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 (B_(gc, red) and X-ray properties are fitted to the data. For systems with measured T_X, we find that optical richness correlates with both T_X 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.