Our models cover a range of orbits and internal structures for the merging galaxies. In all encounters studied, the galaxies experience strong gaseous inflows and, using a density-dependent Schmidt law to model star formation, moderate to intense starburst activity. We find that galaxy structure plays a dominant role in regulating activity. The gaseous inflows are strongest when galaxies with dense central bulges are in the final stages of merging, while inflows in bulgeless galaxies are weaker and occur earlier in the interaction.
Orbital geometry plays only a relatively modest role in the onset of collisionally-induced activity.
To the extent that a Schmidt law is a reasonable description of star formation in these systems, the starbursts which develop in mergers of galaxies with central bulges represent an increase in the star formation rate of two orders of magnitude over that in isolated galaxies. We find that the gaseous and stellar morphology and star-forming properties of these systems provide a good match to those of observed ultraluminous infrared galaxies. Our results imply that the internal structure of the merging galaxies, rather than orbital geometry, may be the key factor in producing ultraluminous infrared galaxies.