Herschel-PACS spectroscopic diagnostics of local ULIRGs: Conditions and kinematics in Markarian 231

Naval Research Laboratory, Remote Sensing Division, 20375, Washington, DC, USA; Max-Planck-Institut für extraterrestrische Physik (MPE), 85741, Garching, Germany; Departamento de Fisica, Universidad de Alcala de Henares, Spain; Sackler School of Physics and Astronomy, Tel Aviv University, 69978, Tel Aviv, Israel; University of Oxford, Denys Wilkinson Building, OX1 3RH, Oxford, UK
Astronomy and Astrophysics (Impact Factor: 4.48). 07/2010; 518. DOI: 10.1051/0004-6361/201014676

ABSTRACT In this first paper on the results of our Herschel PACS survey of local ultra luminous infrared galaxies (ULIRGs), as part of our SHINING survey of local galaxies, we present far-infrared spectroscopy of Mrk 231, the most luminous of the local ULIRGs, and a type 1 broad absorption line AGN. For the first time in a ULIRG, all observed far-infrared fine-structure lines in the PACS range were detected and all were found to be deficient relative to the far infrared luminosity by 1–2 orders of magnitude compared with lower luminosity galaxies. The deficits are similar to those for the mid-infrared lines, with the most deficient lines showing high ionization potentials. Aged starbursts may account for part of the deficits, but partial covering of the highest excitation AGN powered regions may explain the remaining line deficits. A massive molecular outflow, discovered in OH and 18 OH, showing outflow velocities out to at least 1400 km s −1 , is a unique signature of the clearing out of the molecular disk that formed by dissipative collapse during the merger. The outflow is characterized by extremely high ratios of 18 O/ 16 O suggestive of interstellar medium processing by advanced starbursts.

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    ABSTRACT: We report the results from a systematic search for molecular (OH-119 um) outflows with Herschel-PACS in a sample of 43 nearby (z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7-um silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than -50 km/sec, is seen in 26 (70%) of the 37 OH-detected targets, suggesting a wide-angle (~145 degrees) outflow geometry. Conversely, unambiguous evidence for molecular inflows, based on the detection of OH absorption profiles with median velocities more redshifted than +50 km/sec, is seen in only 4 objects, suggesting a planar or filamentary geometry for the inflowing gas. Terminal outflow velocities of ~-1000 km/sec are measured in several objects, but median outflow velocities are typically ~-200 km s^{-1}. While the outflow velocities show no statistically significant dependence on the star formation rate, they are distinctly more blueshifted among systems with large AGN fractions and luminosities [log (L_AGN / L_sun) > 11.8 +/- 0.3]. The quasars in these systems play a dominant role in driving the molecular outflows. In contrast, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.
    The Astrophysical Journal 08/2013; 776(1). · 6.28 Impact Factor

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