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

Abstract

We present ROSAT HRI data of the distant and X-ray-luminous [LX(bol) = 2.6+0.4-0.2 × 1045ergs s-1] cluster of galaxies 3C 295. We fit both a one-dimensional and a two-dimensional isothermal β-model to the data, the latter taking into account the effects of the point spread function (PSF). For the error analysis of the parameters of the two-dimensional model, we introduce a Monte Carlo technique. Applying a substructure analysis by subtracting a cluster model from the data, we find no evidence for a merger, but we see a decrement in emission southeast of the center of the cluster, which might be due to absorption. We confirm previous results by Henry & Henriksen that 3C 295 hosts a cooling flow. The equations for the simple and idealized cooling flow analysis presented here are based solely on the isothermal β-model, which fits the data very well, including the center of the cluster. We determine a cooling flow radius of 60-120 kpc and mass accretion rate of = 400-900 M☉ yr-1, depending on the applied model and temperature profile. We also investigate the effects of the ROSAT PSF on our estimate of , which tends to lead to a small overestimate of this quantity if not taken into account. This increase of (10%-25%) can be explained by a shallower gravitational potential inferred by the broader overall profile caused by the PSF, which diminishes the efficiency of mass accretion. We also determine the total mass of the cluster using the hydrostatic approach. At a radius of 2.1 Mpc, we estimate the total mass of the cluster (Mtot) to be 9.2 ± 2.7 × 1014 M☉. For the gas-to-total mass ratio, we get Mgas/Mtot = 0.17-0.31, in very good agreement with the results for other clusters of galaxies, giving strong evidence for a low-density universe.