Galaxy-Wide Shocks in Late-Merger Stage Luminous Infrared Galaxies
  We present an integral field spectroscopic study of two nearby Luminous
Infrared Galaxies (LIRGs) that exhibit evidence of widespread shock excitation
induced by ongoing merger activity, IC 1623 and NGC 3256. We show the
importance of carefully separating excitation due to shocks vs. excitation by
HII regions and the usefulness of IFU data in interpreting the complex
processes in LIRGs. Our analysis focuses primarily on the emission line gas
which is extensive in both systems and is a result of the abundant ongoing star
formation as well as widespread LINER-like excitation from shocks. We use
emission-line ratio maps, line kinematics, line-ratio diagnostics and new
models as methods for distinguishing and analyzing shocked gas in these
systems. We discuss how our results inform the merger sequence associated with
local U/LIRGs and the impact that widespread shock excitation has on the
interpretation of emission-line spectra and derived quantities of both local
and high-redshift galaxies.
