X-ray Mass Estimates at $z\sim0.3$ for the CNOC Cluster Sample

Results are presented from the analysis of ROSAT HRI and PSPC observations of the CNOC subsample of the EMSS high redshift galaxy clusters. X-ray surface brightness profiles of 14 clusters with 0 . 17 < z < 0 . 55 are constructed and fit to isothermal β models. Where possible, we use both the HRI and PSPC data to constrain the fit. Under the assumptions of isothermality, hydrostatic equilibrium, and spherical symmetry, we derive total X-ray masses within a range of radii from 141 to 526 h − 1 100 kpc. These masses are compared with both the dynamical masses obtained from galaxy velocities and the projected masses from published gravitational lensing studies. We find no systematic bias between X-ray and dynamical methods across the sample, with an average M Dyn /M X = 1 . 04 ± 0 . 07, although individual clusters exhibit mass discrepancies up to a factor of 2. We estimate that the systematic effects due to cooling flows, non-equilibrium systems and temperature gradients affect the average mass ratio by no more than 15 − 20%. Weak gravitational lensing masses appear to be systematically higher than X-ray results by factors of ∼ 50%, while strong lensing estimates show larger discrepancies (factors of ∼ 2 . 5). However, these comparisons are complicated by the need to extrapolate the X-ray data to larger or smaller radii. X-ray derived cluster gas masses are calculated, from which we obtain a cluster baryon fraction of ∼ 5% h − 3 / 2 100 , yielding Ω 0 ∼ 0 . 3 h − 1 / 2 100 .