P. M. S. Namboodiri*
Indian Institute of Astrophysics, Bangalore 560034, India
Abstract. Galaxies interact in a multitude of ways with their environ- ment. Such interactions can alter the morphological type of galaxies, trigger star formation and even produce active galactic nuclei. One of the 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 initial density distribution in the galaxy corresponds that of a polytrope of index n = 4. The galaxy model does not include the dark matter halo component and therefore is not expected to mimic all prop- erties of a real galaxy. Both merging and non-merging collisions of equal mass galaxies have been studied to see where the transition occurs between these two processes. Merging occurs when the closest approach distance of the galaxies is less than three times its half-mass radius. The merging time increases with the distance of closest approach. The density profiles of the merger remnants follow a r1/4 law in the inner parts and deviate from it in the outer regions. Distant encounters do not result in merging and the galaxies remain almost intact with only negligible change in its mass and internal energy.
Keywords: galaxies - dynamics - collisions - numerical simulations