Chandra Sample of Nearby Relaxed Galaxy Clusters: Mass, Gas Fraction, and Mass-Temperature Relation

• Published in: The Astrophysical journal 2006-04, Vol.640 (2), p.691-709
• Main Authors: Vikhlinin, A, Kravtsov, A, Forman, W, Jones, C, Markevitch, M, Murray, S. S, Van Speybroeck, L
• Format: Article
• Language: English
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/500288

We present gas and total mass profiles for 13 low-redshift, relaxed clusters spanning a temperature range 0.7-9 keV, derived from all available Chandra data of sufficient quality. In all clusters, gas-temperature profiles are measured to large radii (Vikhlinin et al.) so that direct hydrostatic mass estimates are possible to nearly r sub(500) or beyond. The gas density was accurately traced to larger radii; its profile is not described well by a beta model, showing continuous steepening with radius. The derived P sub(tot) profiles and their scaling with mass generally follow the Navarro-Frenk-White model with concentration expected for dark matter halos in CDM cosmology. However, in three cool clusters, we detect a central mass component in excess of the Navarro-Frenk-White profile, apparently associated with their cD galaxies. In the inner region (r < 0.1r sub(500)), the gas density and temperature profiles exhibit significant scatter and trends with mass, but they become nearly self-similar at larger radii. Correspondingly, we find that the slope of the mass-temperature relation for these relaxed clusters is in good agreement with the simple self-similar behavior, M sub(500) c T super(a), where a = (1.5-1.6) c 0.1, if the gas temperatures are measured excluding the central cool cores. The normalization of this M-T relation is significantly, by -30%, higher than most previous X-ray determinations. We derive accurate gas mass fraction profiles, which show an increase with both radius and cluster mass. The enclosed f sub(gas) profiles within r sub(2500) super( )0.4r sub(500) have not yet reached any asymptotic value and are still far (by a factor of 1.5-2) from the universal baryon fraction according to the cosmic microwave background (CMB) observations. The f sub(gas) trends become weaker and its values closer to universal at larger radii, in particular, in spherical shells r sub(2500) < r< r sub(500).