ABSTRACT

We model a range of flyby galaxy interactions in order to investigate the formation of starbursts in galaxies with induced stellar bars and/or mass loss or accretion. The models indicate that mass transfer is important in triggering radial gas flows and starburst activity if counter-rotating accretion occurs; i.e., accretion from a prograde disk onto a retrograde disk. Such accretion proves effective in shedding rotational angular momentum of the ISM, resulting in the radial gas flow and subsequent nuclear ISM concentration, while leaving behind a relatively unperturbed stellar disk. However, bar formation proves more important under a wider range of interaction scenarios than does mass transfer, and thus bar formation is the dominant process in triggering nuclear activity in interacting systems as a whole.

INTRODUCTION

The link between galaxy interactions and elevated star formation rates has been demonstrated through observations of such star formation tracers as optical emission lines (e.g., Kennicutt et al 1987; Bushouse 1987), strong far infrared emission (Lonsdale, Persson, and Matthews 1984), and radio continuum emission (Hummel 1981). However, while this large body of evidence indicates that interactions can cause starbursts, it is not at all clear that they must do so. A large fraction of interacting galaxies show little or no increased star formation (Kennicutt et al 1987; Bushouse 1987), suggesting that the triggering mechanism for these starbursts must involve some complicated function of interaction geometry and galaxy properties.