A surviving disk from a galaxy collision at z = 0.4

Abstract

Context. Spiral galaxies dominate the local galaxy population. Disks are known to be fragile to collisions. Thus it is worthwhile to probe under what conditions a disk can possibly survive such interactions.Aims. We present a detailed morpho-kinematic study of a massive galaxy with two nuclei, J033210.76-274234.6, at z = 0.4. Methods. The morphological analysis reveals that the object consists of two bulges and a massive disk, as well as a faint blue ring. Combining the kinematics with morphology we propose a near-center collision model for the object.Results. We find that the massive disk is likely to have survived the collision of galaxies with an initial mass ratio of -4:1. The N-body/Smoothed Particle Hydrodynamics (SPH) simulations show that the collision possibly is a polar collision with a very small pericentric distance of -1 kpc, and that the remnant of the main galaxy will be dominated by a disk. The results support the disk survival hypothesis.Conclusions. The survival of the disk is related to the polar collision with an extremely small pericentric distance. With the help of N-body/SPH simulations we find that the probability of disk survival is quite large regardless of whether the two galaxies merge or not. © 2009 ESO.