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J.S. Mulchaey (Carnegie Observatories)
Recent observations indicate that approximately half of all nearby groups of galaxies contain extended X-ray emission. The most massive groups tend to follow the relationships found for rich clusters between X-ray luminosity, temperature and velocity dispersion. However, there is some evidence that groups with temperatures below about 1 keV depart from the cluster relationships. These departures are often interpreted as evidence for preheating of the intragroup medium by an early generation of stars and supernovae. New velocity dispersion measurements combined with Chandra and XMM observations provide considerable new insight into the X-ray/optical correlations for groups. In addition to these new results at low redshift, I will discuss first results from a sample of X-ray selected groups at moderate redshifts.
The author(s) of this abstract have provided an email address for comments about the abstract: mulchaey@ociw.edu