The energy source and dynamics of infrared luminous galaxy ESO 148-IG002

TL;DR

This study investigates the physical processes in the merging galaxy ESO 148-IG002 using integral field spectroscopy, revealing details about its metallicity, kinematics, and the contributions of star formation, shocks, and AGN activity.

Contribution

It demonstrates the effectiveness of integral field spectroscopy in disentangling the complex emission components in a merging galaxy at a key evolutionary stage.

Findings

Flat metallicity gradient indicates recent gas inflow.

Distinct regions of star formation and high velocity dispersion identified.

Kinematic separation of the two merging galaxies achieved.

Abstract

ESO 148-IG002 represents a transformative stage of galaxy evolution, containing two galaxies at close separation which are currently coalescing into a single galaxy. We present integral field data of this galaxy from the ANU Wide Field Spectrograph (WiFeS). We analyse our integral field data using optical line ratio maps and velocity maps. We apply active galactic nucleus (AGN), star-burst and shock models to investigate the relative contribution from star-formation, shock excitation and AGN activity to the optical emission in this key merger stage. We find that ESO 148-IG002 has a flat metallicity gradient, consistent with a recent gas inflow. We separate the line emission maps into a star forming region with low velocity dispersion that spatially covers the whole system as well as a southern high velocity dispersion region with a coherent velocity pattern which could either be rotation or an AGN-driven outflow, showing little evidence for pure star formation. We show that the two overlapping galaxies can be separated using kinematic information, demonstrating the power of moderate spectral resolution integral field spectroscopy.