X-ray mass estimates at z ∼ 0.3 for the Canadian Network for Observational Cosmology cluster sample

Results are presented from the analysis of ROSAT High-Resolution Imager (HRI) and Position-Sensitive Proportional Counter (PSPC) observations of the Canadian Network for Observational Cosmology (CNOC) subsample of the Extended Medium-Sensitivity Survey (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 beta 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(100)(-1) 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, nonequilibrium 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 similar to 50%, while strong-lensing estimates show larger discrepancies (factors of similar to 2.5). However, these comparisons are complicated by the need to extrapolate the X-ray data to larger or smaller radii. We calculate X-ray-derived cluster gas masses, from which we obtain a cluster baryon fraction of similar to 5% h(100)(-3/2), yielding Omega(0) similar to 0.3 h(100)(-1/2).