Stellar Populations and Collisions of Galaxies.
Abstract
Dense clusters of galaxies, such as the Coma and Corona clusters, coritain large numbers of SO galaxies, which are highly flattened but show no obscuration or spiral structure and presumably contain stars only of population type II. It is suggested that collisions between galaxies sweep any interstellar matter out of the galaxies in such clusters and thereby prevent the appearance of any type I systems. In the Coma cluster each galaxy will collide with at least twenty other galaxies during 3 X 10 years if the galactic motions within the cluster are largely radial. An analysis of galactic collisions shows that two galaxies will interpenetrate freely with relatively little effect on the velocities and positions of the stars in each galaxy but that interstellar matter will be swept completely out of the two galaxies and left in intergalactic space, provided that the initial density is not much lower than 0.1 H atoms per cubic centimeter. Thus highly flattened systems, which might otherwise retain interstellar matter and develop into normal spirals, become pure type II systems.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1951
- DOI:
- 10.1086/145406
- Bibcode:
- 1951ApJ...113..413S