THE FREQUENCY OF MERGERS IN COMPACT-GROUPS

The far-infrared colors, optical morphologies, and emission-line rotation curves of galaxies in compact groups are used to estimate the number of these galaxies which are currently merging. Each of these independent methods indicates that roughly 7% of the galaxies in compact groups are in the process of merging. Although each technique is somewhat uncertain, the agreement among the independent methods for the fraction of ongoing mergers and the generally good correlation between different measures of merging for individual systems lend added weight to the results. The combination of this fraction of galaxies in compact groups which are currently merging with previous studies of the properties of elliptical galaxies in compact groups leads to the conclusion that the dynamical evolution of compact groups through merging occurs on a time scale significantly longer than the observed crossing time.