Title:  Formation of Massive Star Clusters in Interacting Galaxies -
        When, Where, How?



Bill Keel
University of Alabama



Abstract:

I describe a combination of n-body modelling, to derive interaction ages
and orbital parameters of galaxy pairs, with WFPC2 imagery of their star-cluster
systems, to constrain the formation environments of massive "super star clusters".
Such clusters form promptly or not at all after tidal perturbations, with
formation depending strongly on the strength of the perturbation. For example,
the smaller galaxy in a pair may be rich in such clusters while the larger
primary galaxy has no excess star formation. The sites of cluster formation
suggest that Toomre-type disk instabilities, as well as cloud collisions,
may play a role in massive cluster formation. This fits with the occasional
presence of luminous cluster systems in star-forming galaxies without
obvious interactions, and points to an immediate role for perturbations in
the velocity field as a triggering nmechanism. Combined analysis of
ground-based H-alpha data and WFPC2 continuum images allows reconstruction
of cluster ages, and suggest that formation of the cluster population
in low-mass galaxies can be truncated by a global wind.