Morphology of galaxies in compact groups

We report results of a study of galaxy morphology in a homogeneous sample of 98 compact groups of galaxies. Of all the galaxies, 49% are of late morphological type (S + Irr), somewhat less than the corresponding fraction for field galaxies. Similarly, for first-ranked galaxies only, 48%, are late type. There is no significant difference between the distribution of morphological types of first-ranked galaxies and all group galaxies. Several strong correlations are found between galaxy type and the galaxy environment: (1) Morphological concordance occurs between galaxies within a group; We find that in 20 of 58 quartets, all four galaxies have the same general type (early or late). The probability of this occurring by chance is 10^-5^. (2) Galaxy morphological type correlates with group optical luminosity, and (3) galaxy morphology correlates with velocity dispersion. The latter correlation is found to be the more fundamental of the two. We also find no strong correlation between morphological type and galaxy space density in these compact groups, contrary to the situation in rich clusters and loose groups. These results indicate that the morphological types of galaxies in compact groups are strongly influenced by the environment, and that this influence occurs mostly at the time of galaxy formation.