THE MORPHOLOGY AND DARK MATTER DISTRIBUTION OF THE COMA CLUSTER OF GALAXIES FROM X-RAY OBSERVATIONS

The analysis of a spectral image of the Coma cluster obtained with a coded mask telescope flown as part of the Spacelab 2 mission is presented. The main cluster emission is elongated east-west and extends to a radius of at least 50 arcmin, while an additional region of X-ray emission is detected approximately 50 arcmin to the south-west of the cluster centre. The energy range of the instrument and its imaging capabilities allow the temperature and density of the intracluster gas to be determined as a function of radius, and thus allow the total cluster mass profile to be determined. We find that the gas temperature profile is consistent with an isothermal model, and derive a cluster binding mass of 4.2-5.2 x 10(14) h50(-1) M. within 1 h50(-1) Mpc (24 arcmin) of the cluster centre, the most accurate determination to date. We find no evidence for variation of metallicity with radius. This result differs from that obtained for the Perseus cluster; we suggest that the two clusters have different evolutionary histories, and that the Coma cluster has recently undergone a merger which has disrupted the pre-existing cluster conditions.