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Date and Time of the Query: 2018-11-14 T01:03:03 PST
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For refcode 1995ApJ...443..514P:
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1995ApJ...443..514P ROSAT OBSERVATIONS OF COMPACT GROUPS OF GALAXIES RACHEL A. PILDIS AND JOEL N. BREGMAN Department of Astronomy, University of Michigan. Ann Arbor, MI 48109-1090; pildis,jbregman@astro.lsa.umich.edu AND AUGUST E. EVRARD Department of Physics, University of Michigan, Ann Arbor, MI 48109-1120; evrard@umich.edu Received 1994 July 28; accepted 1994 October 27 ABSTRACT We have systematically analyzed a sample of 13 new and archival ROSAT Position Sensitive Proportional Counter observations of compact groups of galaxies: 12 Hickson compact groups plus the NCG 2300 group. We find that approximately two-thirds of the groups have extended X-ray emission and, in four of these, the emission is resolved into diffuse emission from gas at a temperature of kT~1 keV in the group potential. All but one of the groups with extended emission have a spiral fraction of less than 50%. The baryon fraction of groups with diffuse emission is 5%-19%, similar to the values in clusters of galaxies. However, with a single exception (HCG 62), the gas-to-stellar mass ratio in our groups has a median value near 5%, somewhat greater than the values for individual early-type galaxies and two orders of magnitude than in clusters of galaxies. The X- ray luminosities of individual group galaxies are comparable to those of similar field galaxies, although the L_X_-L_B_ relation for early-type galaxies may be flatter in compact groups than in the field. Subject headings: diffuse radiation - galaxies: clusters: general - X- rays: galaxies
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