Sharp Edges Due to Close Interactions
Sharp edges of spiral arms, found in simulations and observations of galaxies in interaction, are explained kinematically using the impulse approximation. We investigate the kinematics of a galactic disc perturbed by a disturber on an unbound orbit. Such encounters can be expected to be common if galaxies are initially formed in weakly bound, low angular momentum systems. Here we shall be concerned with smaller disturbing masses (less than 10 % of the main galaxy) as larger disturbances will tend to disrupt the disc. We present results for the case of a 5 % disturber passing through the outer parts of a Kuzmin disc.