Studying the kinematic asymmetries of disks and post-coalescence mergers using a new `kinemetry' criterion

TL;DR

This study uses a new kinematic analysis method to distinguish between disk galaxies and post-coalescence mergers, revealing that previous classifications may have underestimated merger prevalence due to resolution sensitivities.

Contribution

The paper introduces a novel kinematic criterion based on kinemetry to more accurately differentiate disks from post-coalescence mergers, reducing sensitivity to resolution effects.

Findings

Kinematic maps show consistency with morphological classifications.

New criterion better separates disks from mergers.

Previous methods may have underestimated merger numbers.

Abstract

We have obtained VIMOS/VLT optical integral field spectroscopy (IFS) data for a sample of 4 LIRGs which have been selected at a similar distance ($\sim$ 70 Mpc) to avoid relative resolution effects. They have been classified in two groups (isolated disk and post-coalescence mergers) according to their morphology. The $kinemetry$ method (developed by Krajnovic and coworkers) is used to characterize the kinematic properties of these galaxies and to discuss new criteria for distinguishing their status. We present and discuss new kinematic maps (i.e., velocity field and velocity dispersion) for these four galaxies. The morphological and kinematic classifications of these systems are consistent, with disks having lower kinematic asymmetries than post-coalescence mergers. We then propose and discuss a new kinematic criterion to differentiate these two groups. This criterion distinguishes better these two categories and has the advantage of being less sensitive to angular resolution effects. According to the previous criteria,the present post-coalescence systems would have been classified as disks. This indicates that the separation of disks from mergers is subjective to the definition of `merger'. It also suggests that previous estimates of the merger/disk ratio could have been underestimated, but larger samples are necessary to establish a firmer conclusion.