Investigation of Dual Active Nuclei, Outflows, Shock-Heated Gas, and
  Young Star Clusters in Markarian 266
  Results of observations with the Spitzer, Hubble, GALEX, Chandra, and
XMM-Newton space telescopes are presented for the Luminous Infrared Galaxy
(LIRG) merger Mrk 266. The SW (Seyfert 2) and NE (LINER) nuclei reside in
galaxies with Hubble types SBb (pec) and S0/a (pec), respectively. Both
galaxies have L > L*, and they are inferred to each contain a ~2.5x10^8 M_sun
black hole. Mrk 266 SW is likely the primary source of a bright Fe K-alpha line
detected from the system, consistent with the reflection-dominated X-ray
spectrum of a heavily obscured AGN. Optical knots embedded in an arc with
aligned radio continuum radiation, combined with luminous H_2 line emission,
provide evidence for a radiative bow shock in an AGN-driven outflow surrounding
the NE nucleus. Soft X-ray emission modeled as shock-heated plasma is
co-spatial with radio continuum emission between the galaxies. Mid-IR
diagnostics indicate roughly equal contributions of AGN and starburst radiation
powering the bolometric luminosity. Approximately 120 star clusters have been
detected, with most having estimated ages < 50 Myr. Detection of 24 micron
emission extending ~34 arcsec (20 kpc) north of the galaxies is interpreted as
~2x10^7 M_sun of dust entrained in an outflowing superwind; at optical
wavelengths this region is resolved into a fragmented morphology indicative of
Rayleigh-Taylor instabilities in an expanding shell of ionized gas. Mrk 266
demonstrates that the dust "blow-out" phase can begin in a LIRG well before the
galaxies fully coalesce during a subsequent ULIRG phase, and rapid gas
consumption in luminous dual AGNs (kpc scale separations) early in the merger
process may explain the paucity of detected binary QSOs (sub-pc scale orbits)
in large surveys. An evolutionary sequence is proposed representing a
progression from dual to binary AGNs, accompanied by an increase in observed
L_x/L_ir ratios by 10^4 or more.
