<i>Chandra</i>Sample of Nearby Relaxed Galaxy Clusters: Mass, Gas Fraction, and Mass‐Temperature Relation

Abstract

We present gas and total mass profiles for 13 low-redshift, relaxed clusters\nspanning a temperature range 0.7-9 keV, derived from all available Chandra data\nof sufficient quality. In all clusters, gas temperature profiles are measured\nto large radii (Vikhlinin et al.) so that direct hydrostatic mass estimates are\npossible to nearly r_500 or beyond. The gas density was accurately traced to\nlarger radii; its profile is not described well by a beta-model, showing\ncontinuous steepening with radius. The derived rho_tot profiles and their\nscaling with mass generally follow the Navarro-Frenk-White model with\nconcentration expected for dark matter halos in LambdaCDM cosmology. In the\ninner region (r&lt;0.1r_500), the gas density and temperature profiles exhibit\nsignificant scatter and trends with mass, but they become nearly self-similar\nat larger radii. Correspondingly, we find that the slope of the\nmass-temperature relation for these relaxed clusters is in good agreement with\nthe simple self-similar behavior, M_500 ~ T^alpha, where alpha=(1.5-1.6)+-0.1,\nif the gas temperatures are measured excluding the central cool cores. The\nnormalization of this M-T relation is significantly, by =~ 30%, higher than\nmost previous X-ray determinations. We derive accurate gas mass fraction\nprofiles, which show increase both with radius and cluster mass. The enclosed\nf_gas profiles within r_2500 =~ 0.4 r_500 have not yet reached any asymptotic\nvalue and are still far (by a factor of 1.5-2) from the Universal baryon\nfraction according to the CMB observations. The f_gas trends become weaker and\nits values closer to Universal at larger radii, in particular, in spherical\nshells r_2500&lt;r&lt;r_500.\n