A surviving disk from a galaxy collision at z=0.4

TL;DR

This study investigates how a massive galaxy disk can survive a collision at z=0.4, using detailed observations and simulations, suggesting that certain collision conditions allow disk preservation.

Contribution

The paper demonstrates that a galaxy disk can survive a near-center polar collision with a small pericentric distance, supported by morpho-kinematic analysis and N-body/SPH simulations.

Findings

The galaxy's disk likely survived a 4:1 mass ratio collision.

A polar collision with a small pericenter can preserve the disk.

Simulations indicate a high probability of disk survival regardless of merging.

Abstract

Spiral galaxies dominate the local galaxy population. Disks are known to be fragile with respect to collisions. Thus it is worthwhile to probe under which conditions a disk can possibly survive such interactions. We present a detailed morpho-kinematics study of a massive galaxy with two nuclei, J033210.76--274234.6, at z=0.4. 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 to interpret the object. 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/SPH simulations show that the collision possibly is a single-shot 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. 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 the probability of disk survival is quite large regardless whether the two galaxies merge or not.