INVESTIGATION OF DUAL ACTIVE NUCLEI, OUTFLOWS, SHOCK-HEATED GAS, AND YOUNG STAR CLUSTERS IN MARKARIAN 266

Abstract

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