3C 295: A Cluster and Its Cooling Flow atz= 0.46

We present ROSAT HRI data of the distant and X-ray luminous (L_x(bol)=2.6^{+0.4}_{-0.2} 10^{45}erg/sec) cluster of galaxies 3C 295. We fit both aone-dimensional and a two-dimensional isothermal beta-model to the data, thelatter one taking into account the effects of the point spread function (PSF).For the error analysis of the parameters of the two-dimensional model weintroduce a Monte-Carlo technique. Applying a substructure analysis, bysubtracting a cluster model from the data, we find no evidence for a merger,but we see a decrement in emission South-East of the center of the cluster,which might be due to absorption. We confirm previous results by Henry &Henriksen(1986) that 3C 295 hosts a cooling flow. The equations for the simpleand idealized cooling flow analysis presented here are solely based on theisothermal beta-model, which fits the data very well, including the center ofthe cluster. We determine a cooling flow radius of 60-120kpc and mass accretionrates of dot{M}=400-900 Msun/y, depending on the applied model and temperatureprofile. We also investigate the effects of the ROSAT PSF on our estimate ofdot{M}, which tends to lead to a small overestimate of this quantity if nottaken into account. This increase of dot{M} (10-25%) can be explained by ashallower gravitational potential inferred by the broader overall profilecaused by the PSF, which diminishes the efficiency of mass accretion. We alsodetermine the total mass of the cluster using the hydrostatic approach. At aradius of 2.1 Mpc, we estimate the total mass of the cluster (M{tot}) to be(9.2 +/- 2.7) 10^{14}Msun. For the gas to total mass ratio we get M{gas}/M{tot}=0.17-0.31, in very good agreement with the results for other clusters ofgalaxies, giving strong evidence for a low density universe.Comment: 26 pages, 7 figures, accepted for publication in Ap