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.
Highlights
In the local universe, most of the intermediate-mass galaxies are spiral galaxies (Nakamura et al 2004) that have experienced a violent merging stage over the last 8 Gyr (Le Fèvre et al 2000; Bundy et al 2004; Rawat et al 2008)
The morphological analysis reveals that the object consists of two bulges and a massive disk, as well as a faint blue ring
We find that the massive disk is likely to have survived the collision of galaxies with an initial mass ratio of ∼4:1
Summary
Most of the intermediate-mass galaxies are spiral galaxies (Nakamura et al 2004) that have experienced a violent merging stage over the last 8 Gyr (Le Fèvre et al 2000; Bundy et al 2004; Rawat et al 2008). Hammer et al (2005) propose a scenario of “disk-rebuilding” based on the remarkable coincidence of the evolution of the merger rate, morphology and fraction of actively star-forming galaxies. In such a scenario, a significant fraction of galaxies experienced their last major merger during the last 8 Gyr, by accretion of gas and debris, the disks were formed around the merger remnants. One interesting galaxy interaction is head-on collision which may cause the formation of the ring in disk galaxies, so called “collisional” ring galaxies (Lynds & Toomre 1976). 2 we describe the data we have obtained for the object; in Sect.
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