Simulations of Merging Galaxies.

A large number of numerical simulations of merging disk - halo galaxies has been performed for a wide variety of initial conditions and parameter choices. The disks of these galaxies contain a "gaseous" component which, using a newly developed algorithm, is modelled as a collection of variable radius spheres capable of undergoing inelastic collisions. Galaxies on initially bound or marginally unbound orbits interact strongly and eventually merge; the details of this interaction and the properties of merger remnants are studied extensively. The remnants are ellipsoidal and have a wide range of principal axis flattenings which depend on the pericentric distance of the initial orbit and on the orientation of the initial disk spins; they show r('-2) projected "luminosity" profiles and flat rotation curves, in agreement with observations of elliptical galaxies. If elliptical galaxies are remnants of such mergers, the low observed rotation velocities then suggest a preponderance of low angular momentum mergers; if this is the case, our results favour the hypothesis that elliptical galaxies are intrinsically prolate or triaxial.