Dying of the Light: An X-ray Fading Cold Quasar at z ~ 0.405
  Cold quasars are a rare subpopulation observed to host unobscured, X-ray
luminous active galactic nuclei (AGN) while also retaining a cold gas supply
fueling high star formation rates. These objects are interpreted as AGN early
in their evolution. We present new SOFIA HAWC+ far-infrared observations,
FUV-FIR photometry, and optical spectroscopy to characterize the accretion and
star formation behavior in a cold quasar at z ~ 0.405 (CQ 4479). CQ 4479 is a
starburst galaxy with a predominantly young stellar population and a high gas
mass fraction of ~50-70%. The AGN component has yet to become the dominant
component of the FIR emission. We also find AGN bolometric luminosity that
varies as a function of observation method and AGN region probed. Finally, we
identify a candidate outflow feature corroborating the hypothesis that cold
quasars have energetic feedback. This object presents an intriguing look into
the early stages of AGN feedback and probes the rare phase where an AGN and
cold gaseous component co-exist.
