Advanced mergers of galaxies: luminosity profiles and dynamics

Abstract

We have analyzed the near-IR Ks-band data from the 2MASS archival database for a large sample of twenty-seven galaxies that show signs of interaction but have a single nucleus. Surprisingly, half of these advanced mergers of galaxies show luminosity profiles which have an outer exponential fall-off with radius, as in a spiral galaxy (Chitre and Jog 2002). The kinematical data for two of these, Arp 224 and Arp 214, available from the HYPERCAT database were used and these show kinematics similar to elliptical galaxies with the random motion dominating the rotation (Jog and Chitre 2002). The origin of the mixed properties shown by these mergers is a puzzle. To understand these systems, we have recently studied the dynamics of mergers via N-body simulations for unequal-mass mergers covering a new range of galaxy mass ratios 4:1-10:1 (Bournaud, Combes, and Jog 2004). We show that such mergers naturally result in remnants that have the mixed properties as we have observed from the 2MASS data analysis. The transition between elliptical and disk-like remnants is found to occur over a narrow range of galaxy mass ratios 3:1-4.5:1 (Bournaud, Jog and Combes 2005)