Mathematical sciences: The dynamics of Colliding Galaxies

Abstract

Galaxies interact in a multitude of ways with their environment. Such interactions can alter the morphological type of galaxies, trigger star formation and even produce active galactic nuclei. During the past three decades computer simulations have been extensively used to study the dynamics of colliding galaxies. Galactic collision is essentially an N-body problem where N represents the number stars in a galaxy. The most important parameter in a galaxy collision is the impact parameter. Numerical simulations have been performed to study the effect of changing the impact parameter in a galactic collision. The density distribution in the galaxy corresponds to that of a polytrope of index n = 4. Both merging and non-merging collisions of galaxies have been studied to see where the transition occurs between these two processes. Merging occurs when the distance of closest approach of the galaxies is less than three times its half-mass radius. The density profiles of the merger remnants follow a r/sup1/4/ law. Distant encounters do not result in merging and the galaxies remain almost in tact with only negligible change in its mass and internal energy.