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