MODELING THE SPATIAL-DISTRIBUTION OF STAR-FORMATION IN INTERACTING DISK GALAXIES

Models of star-forming interacting galaxies are combined with observational data to investigate the nature of star formation in interacting and merging disk galaxies. Detailed models of specific interacting systems are created using the observed morphology and kinematics of the system to constrain model parameters describing the interaction. The models employ an N-body code to calculate the gravitational dynamics, a discrete cloud model to govern the ISM dynamics, and a modified Schmidt law to describe star formation. To compare the models to the observed systems, new observations of three interacting systems-NGC 4676, IC 1908, and NGC 6872/IC 4970-are presented, along with observations of NGC 4038/39 and NGC 7252 culled from the literature. The resulting modeled star-forming properties of each system are then compared to observed star formation tracers such as the spatial distribution of Halpha and the total far-infrared luminosity. We find that the models describe the star-forming properties of several observed systems reasonably well in terms of the relative intensity and morphology of induced star formation. In several cases, however, the models underestimate the star formation rate in regions where the ISM is presumed to be experiencing a strong collision, suggesting that collisionally induced star formation may play an important role in such regions. Furthermore, strong star formation is observed in regions of high-velocity dispersion and velocity gradients in Fabry-Perot observations of both IC 1908 and NGC 6872. Finally, the relatively mild modeled starbursts in the merging systems again show the difficulty in triggering starbursts intense enough to drive the emission from ultraluminous infrared galaxies. In order to trigger such activity via merger-induced star formation, the merger must occur rapidly and involve extremely gas rich disks.