X-Ray Mass Estimates at Z ~ 0.3 for the Canadian Network for Observational Cosmology Cluster Sample
Abstract
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 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-1100 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 MDyn/MX=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 ~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. We calculate X-ray-derived cluster gas masses, from which we obtain a cluster baryon fraction of ~5% h-3/2100, yielding Ω0~0.3 h-1/2100.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 1999
- DOI:
- 10.1086/307204
- arXiv:
- arXiv:astro-ph/9901062
- Bibcode:
- 1999ApJ...517..587L
- Keywords:
-
- GALAXIES: COOLING FLOWS;
- COSMOLOGY: OBSERVATIONS;
- GALAXIES: CLUSTERS: GENERAL;
- GALAXIES: FUNDAMENTAL PARAMETERS;
- COSMOLOGY: GRAVITATIONAL LENSING;
- Galaxies: Cooling Flows;
- Cosmology: Observations;
- Galaxies: Clusters: General;
- Galaxies: Fundamental Parameters;
- Cosmology: Gravitational Lensing;
- Astrophysics
- E-Print:
- 39 pages, AASTex 4.0, 11 figures, postscript. Accepted for publication in the Astrophysical Journal