Star clusters driven to form by strong collisions between gas clouds in high-velocity random motion

Two topics are discussed about the globular and populous star clusters, based on an idea that they were/are driven to form through strong collisions between massive gas clouds in high-velocity random motion. The first is a global trial to reproduce the approximately-constant specific frequency of globular clusters among normal elliptical galaxies: The ratio of the total number of globular clusters to the luminosity of their host galaxy is obtained to be approximately constant by counting the number of collisions between gas clouds in virialized motion in the gravitational potential of the protogalaxy. The second is presenting a local dynamical model for the formation of binary star clusters such as detected numerously in the Magellanic Clouds. It is stressed that the oblique cloud-cloud collisions occur more frequently than the head-on collisions, and the former collisions yield shear and rotation to the compressed gaseous slab, which works to split a local Jeans gas clump into two objects revolving around each other (fission). In order to examine this dynamical model for the binary star cluster formation, we determine numerical values of the split objects, such as their mass, diameter of revolution, frequency of occurrence, etc., to be compared with those measured in the Large Magellanic Cloud. (C) 1997 American Astronomical Society.