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For refcode 1999ApJ...517..587L:
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1999ApJ...517..587L X-Ray Mass Estimates at z ~ 0.3 for the Canadian Network for Observational Cosmology Cluster Sample AARON D. LEWIS AND E. ELLINGSON Center for Astrophysics and Space Astronomy, University of Colorado at Boulder, Campus Box 389, Boulder, CO, 80309 SIMON L. MORRIS National Research Council of Canada, Herzberg Institute of Astrophysics, Dominion Astrophysical Observatory, 5071 West Saanich Road, Victoria, B.C., V8X 4M6, Canada AND R. G. CARLBERG Department of Astronomy, University of Toronto, Toronto, Ontario, M5S 1A7 Canada Received 1997 December 3; accepted 1999 January 10 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 {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 ~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_100_^- 3/2^, yielding {OMEGA}_0_ ~ 0.3 h_100_^-1/2^. Subject headings: cooling flows-cosmology: observations-galaxies: clusters: general-galaxies: fundamental parameters-gravitational lensing
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