THE X-RAY COOLING FLOW IN THE CLUSTER OF GALAXIES AROUND PKS-2354-35

A position measured with the HEAO 1 Scanning Modulation collimator suggested the group of galaxies surrounding the radio galaxy PKS 2354-35 as the identification of the bright, hard X-ray source 4U 0009-33 = 3A 2356-341 = 1H 2355-350. We confirm this identification with measurements of the position and spatial extent using the EXOSAT CMA detector. It shows centrally condensed X-ray emission which is distinctly asymmetric, with a core radius approximately 7'.3 in a roughly N-S direction and approximately 2'.5 in the E-W direction. A serendipitous Einstein IPC detection confirms the shape of this extent. The EXOSAT ME data are fitted by a thermal bremsstrahlung spectrum with a temperature of 3.7 +/- 0.7 keV. Previously, PKS 2354-35 had been found to be a cD galaxy in a small group at redshift 0.048. At this distance the 2-6 keV X-ray luminosity is 1.6 x 10(44) ergs s-1. Our own optical observations reveal strong, narrow (< 1000 km s-1) emission lines of [O II] and [N II] with luminosities approximately 10(41) ergs s-1. Archival radio observations from the partially completed VLA discovered a 35" long, jetlike component, nearly aligned with the major axis of the X-ray distribution. The high-frequency radio spectrum of the total source is very steep, with a special index of 1.6 in the 1.4-5 GHz band. From the X-ray observations we deduce a strong accretion flow. The luminosity and core radius imply a central density at least 8 x 10(-3) cm-3. The central cooling time is no longer than 5 x 10(9) yr, and the mass accretion rate can be estimated roughly as 320 M. yr-1.