Tidal interaction between a disc galaxy and a spherical galaxy

Abstract

The tidal interaction between a disk and a Plummer model spherical galaxy is studied, extending the impulsive approximation theory to disk galaxies. The fractional change in the internal energy and merger velocities for the disk-sphere pair is determined for various disk orientations. The ratio of the actual velocity of escape, taking the tidal effects into account, and the parabolic velocity of escape of the two galaxies at zero separation is found (for head-on collision) to be virtually independent of model density and disk inclination. The chance of two spherical galaxies merging in a head-on collision due to tidal capture is shown, in the present model, to be greater than that for a disk-sphere pair