The Rotation of Groups of Galaxies

The groups with 10 to 16 members and with almost symmetrical distribution of galaxies in relation to their small and large axes, which could be dynamically confined and not contaminated with interlopers and projected field galaxies, are selected for study. The average velocities of member galaxies at two sides of the small and large axes of these groups are compared with their velocity dispersions. Additionally, the dependence of the group elongation (the b/a ratio) on the velocity dispersion is discussed. It is shown that members of about 10% ÷ 25% of the studied groups move along the group elongation; hence these groups are rotating. Possible rotation of other groups could also be detected, if to exclude interlopers and projected galaxies.