The AGN Luminosity Fraction in Merging Galaxies
  Galaxy mergers are key events in galaxy evolution, often causing massive
starbursts and fueling active galactic nuclei (AGN). In these highly dynamic
systems, it is not yet precisely known how much starbursts and AGN respectively
contribute to the total luminosity, at what interaction stages they occur, and
how long they persist. Here we estimate the fraction of the bolometric infrared
(IR) luminosity that can be attributed to AGN by measuring and modeling the
full ultraviolet to far-infrared spectral energy distributions (SEDs) in up to
33 broad bands for 24 merging galaxies with the Code for Investigating Galaxy
Emission. In addition to a sample of 12 confirmed AGN in late-stage mergers,
found in the $Infrared$ $Array$ $Satellite$ Revised Bright Galaxy Sample or
Faint Source Catalog, our sample includes a comparison sample of 12 galaxy
mergers from the $Spitzer$ Interacting Galaxies Survey, mostly early-stage. We
perform identical SED modeling of simulated mergers to validate our methods,
and we supplement the SED data with mid-IR spectra of diagnostic lines obtained
with $Spitzer$ InfraRed Spectrograph. The estimated AGN contributions to the IR
luminosities vary from system to system from 0% up to 91% but are significantly
greater in the later-stage, more luminous mergers, consistent with what is
known about galaxy evolution and AGN triggering.
