Computer Modelling of the Gas Dynamics in Small Groups of Interacting Galaxies

Abstract

Previous attempts to model interacting galaxies using computers have typically used particles either moving under the influence of external potentials and/or the potential of the particles themselves. The range of approaches to this problem is large; from the simple Toomre three body models (Toomre and Toomre, 1972) to the complex, self-consistent models of Miller and Smith (1980). Although these models represent the dynamics of the stellar component of galaxies there is good reason to believe that the gas component will have a very different behaviour. The dynamics of the gas will differ from the dynamics of the particles because of the effect of pressure forces; this means, for instance, that colliding gas clouds will interact more strongly than colliding particle clouds. Observationally also there is evidence for this different behaviour; Appleton (c.f. this conference) has described the interacting galaxy NGC4747 which has a gaseous plume and a stellar plume which are offset from one-another. Observations of the M81/M82 system (Appleton et al, 1981) show it to have very extended HI emission, suggesting the gas has been affected by the interaction more strongly than the stars.