Relative velocities of dumbbell galaxies.
Abstract
We present a systematic study of a morphologically-selected sample of dumbbell galaxies. For 44 objects meeting strict classification criteria we have accumulated redshifts, velocity differences and projected separations. Many of the redshifts and of the separations are new measurements. A dumbbell/multiple nuclei subclassification scheme is introduced. The single-object velocity dispersion of dumbbell components in Abell-type clusters is 436+/-88 km s^-1^, which is significantly smaller than that of normal cluster galaxies and of multiple nuclei systems. A detailed analysis of this sample, taking into account various projection effects, indicates that the two components of dumbbell pairs are physically associated, and probably in circular orbits around a common center. A relative rotation velocity of 1200 km s^-1^ at a separation of 40 kpc is indicated. This translates into a single-object velocity of 600 km s^-1^, intermediate between the typical rotation velocity in the central part of a cD galaxy and that in the cluster-at-large. Furthermore, the rotation curve appears to be rising in this radial range. Our data provide direct evidence of the existence of a dark intracluster medium on a scale of 20-50 kpc.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1988
- Bibcode:
- 1988A&A...206...27V
- Keywords:
-
- Galactic Clusters;
- Galactic Structure;
- Interacting Galaxies;
- Dark Matter;
- Galactic Nuclei;
- Red Shift;
- Velocity Distribution;
- Astrophysics