Disentangling the morpho-kinematic properties of a face-on merger at z~0.7

TL;DR

This study combines morphological, kinematical, and simulation analyses to understand a face-on galaxy merger at z~0.7, highlighting the importance of kinematic data in correctly interpreting galaxy interactions.

Contribution

It provides a detailed case study of a face-on merger at intermediate redshift, demonstrating the necessity of kinematic data for accurate interpretation of galaxy interactions.

Findings

Identified a face-on disk galaxy with a bright bar interacting with a smaller companion.

Demonstrated the importance of kinematic information in correctly interpreting galaxy morphology.

Used simulations to test and support the proposed interaction scenario.

Abstract

At intermediate redshifts, many galaxies seem to be perturbed or suffering from an interaction. Considering that disk galaxies may have formed and evolved through minor mergers or through major mergers, it is important to understand the mechanisms at play during each type of merger in order to be able to establish the outcome of such an event. In some cases, only the use of both morphological and kinematical information can disentangle the actual configuration of an encounter at intermediate redshift. In this work, we present the morphological and kinematical analysis of a system at z=0.74 in order to understand its configuration, interacting stage and evolution. Using the integral field spectrograph GIRAFFE, long-slit spectroscopy by FORS2 and direct optical images from the HST-ACS and ISAAC near-infrared images, we disentangle the morphology of this system, its star-formation history and its extended kinematics in order to propose a possible configuration for the system. Numerical simulations are used to test different interacting scenarii. We identify this system as a face-on disk galaxy with a very bright bar in interaction with a smaller companion with a mass ratio of 3:1. The relevance of kinematical information and the constraints it imposes on the interpretation of the observations of distant galaxies is particularly strengthened in this case. This object is amongst the best example on how one may misinterpret morphology in the absence of kinematical information.