ROSAT Observations of Compact Groups of Galaxies
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1995
- DOI:
- 10.1086/175544
- arXiv:
- arXiv:astro-ph/9501004
- Bibcode:
- 1995ApJ...443..514P
- Keywords:
-
- Diffuse Radiation;
- Galactic Clusters;
- Gravitation;
- Interstellar Gas;
- Luminosity;
- Mass;
- X Ray Astronomy;
- Astronomical Maps;
- Baryons;
- Computer Programs;
- Heao 2;
- Proportional Counters;
- Rosat Mission;
- X Ray Telescopes;
- Astrophysics;
- COSMOLOGY: DIFFUSE RADIATION;
- GALAXIES: CLUSTERS: GENERAL;
- X-RAYS: GALAXIES;
- Astrophysics
- E-Print:
- 27 pages in AASTeX format, figures available from pildis@astro.lsa.umich.edu