A surviving disk from a galaxy collision at z = 0.4

¹ GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, 5 Place Jules Janssen, Meudon, France e-mail: yanbin.yang@obspm.fr
² ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany

Received: 10 July 2008
Accepted: 1 April 2009

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 .

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.