First detection of a minor merger a z~0.6

TL;DR

This paper reports the first direct detection of a minor galaxy merger at redshift ~0.6 using combined photometric and kinematic data, highlighting 3D spectroscopy's effectiveness in identifying such events.

Contribution

It provides the first direct evidence of a minor merger at z~0.6 through combined imaging and 3D spectroscopy analysis, demonstrating a new method for detecting minor mergers.

Findings

Detected a minor merger with a mass ratio of ~1:18 at z~0.6.

Minor mergers can explain perturbed kinematics in rotating disks.

3D spectroscopy is effective for identifying minor mergers in distant galaxies.

Abstract

Numerical simulations predict that minor mergers are an important channel for the mass assembly of galaxies. However, minor mergers are relatively difficult to detect using imaging, especially at high redshift. While such events are much less violent than major mergers, they can nevertheless leave several features on the kinematical structures of remnant galaxies which could be detected using 3D spectroscopy. We present the first direct detection of a minor merger in a z~0.6 galaxy. Such events could indeed be good candidates to explain the kinematics of perturbed rotating disks observed with GIRAFFE at z~0.6. We present photometric and kinematical evidence of such an event in a combined analysis of three-band HST/ACS imaging and VLT/GIRAFFE 2D-kinematics. Using these data, we are able to demonstrate that a minor merger of a relatively small satellite (mass ratio ~1:18) is occurring in this galaxy. We also derive a total SFR ~21Mo/yr. Minor mergers could be one of the physical processes explaining the kinematics of perturbed rotating disks, which represent ~25% of emission line intermediate mass galaxies at z~0.6. 3D spectroscopy appears to be a very good tool to identify minor mergers in distant (and local) galaxies.