A combined X-ray and gravitational lensing study of the massive cooling-flow cluster PKS 0745-191

We present spatially resolved X-ray spectroscopy of the X-ray-luminous cluster of galaxies, PKS 0745 - 191, using observations made with the ASCA and ROSAT satellites. The X-ray data measure the temperature, density and metallicity of the intracluster medium (ICM) as a function of radius, and determine the total mass profile within similar to 1.5 Mpc of the cluster centre. The ASCA data show that the central ICM is significantly multiphase. The spectral and imaging X-ray data confirm that PKS 0745 - 191 contains one of the largest known cooling flows, with a mass deposition rate of similar to 1000 M. yr(-1). We also report the discovery, from optical studies, of a bright, gravitationally lensed are, at a redshift z(arc) = 0.433, in the cluster. This result identifies PKS 0745 - 191 as the lowest redshift cluster (z(clus) = 0.1028) known to exhibit gravitational lensing. The properties of the lensed source are consistent with an Sab galaxy with ongoing star formation. The cluster mass, determined from lensing arguments, is in excellent agreement with the value determined from a multiphase analysis of the X-ray data. This contrasts with previously reported results for the clusters Abell 1689 and 2218, for which discrepancies of similar to a factor 2 in the lensing and X-ray masses are inferred.