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Browsing by Author "Lebouteiller, V."

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    Diagnostics of AGN-driven molecular outflows in ULIRGs from Herschel-PACS observations of OH at 119 μm
    Spoon, H. W. W.; Farrah, D.; Lebouteiller, V.; Gonzalez-Alfonso, E.; Bernard-Salas, J.; Urrutia, T.; Rigopoulou, D.; Westmoquette, M. S.; Smith, H. A.; Afonso, J.; Pearson, C.; Cormier, D.; Efstathiou, A.; Borys, C.; Verma, A.; Etxaluze, M.; Clements, D. L. (IOP Publishing Ltd., 2013-10)
    We report on our observations of the 79 and 119 mu m doublet transitions of OH for 24 local (z < 0.262) ULIRGs observed with Herschel-PACS as part of the Herschel ULIRG Survey (HERUS). Some OH 119 mu m profiles display a clear P-Cygni shape and therefore imply outflowing OH gas, while other profiles are predominantly in absorption or are completely in emission. We find that the relative strength of the OH emission component decreases as the silicate absorption increases. This result locates the OH outflows inside the obscured nuclei. The maximum outflow velocities for our sources range from less than 100 to similar to 2000 km s(-1), with 15/24 (10/24) sources showing OH absorption at velocities exceeding 700 km s(-1) (1000 km s(-1)). Three sources show maximum OH outflow velocities exceeding that of Mrk231. Since outflow velocities above 500-700 km s(-1) are thought to require an active galactic nucleus (AGN) to drive them, about two-thirds of our ULIRG sample may host AGN-driven molecular outflows. This finding is supported by the correlation we find between the maximum OH outflow velocity and the IR-derived bolometric AGN luminosity. No such correlation is found with the IR-derived star formation rate. The highest outflow velocities are found among sources that are still deeply embedded. We speculate that the molecular outflows in these sources may be in an early phase of disrupting the nuclear dust veil before these sources evolve into less-obscured AGNs. Four of our sources show high-velocity wings in their [C II] fine-structure line profiles, implying neutral gas outflow masses of at least (2-4.5) x 10(8) M-circle dot.
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    Far-infrared fine-structure line diagnostics of ultraluminous infrared galaxies
    Farrah, D.; Lebouteiller, V.; Spoon, H. W. W.; Bernard-Salas, J.; Pearson, C.; Rigopoulou, D.; Smith, H. A.; Gonzalez-Alfonso, E.; Clements, D. L.; Efstathiou, A.; Cormier, D.; Afonso, J.; Petty, S. M.; Harris, K.; Hurley, P.; Borys, C.; Verma, A.; Cooray, A.; Salvatelli, V. (IOP Publishing Ltd., 2013-10)
    We present Herschel observations of 6 fine-structure lines in 25 ultraluminous infrared galaxies at z < 0.27. The lines, [O III]52 mu m, [N III] 57 mu m, [O I]63 mu m, [N II]122 mu m, [O I]145 mu m, and [C II]158 mu m, are mostly single Gaussians with widths < 600 km s(-1) and luminosities of 10(7)-10(9) L-circle dot. There are deficits in the [O I] 63/L-IR, [N II]/L-IR, [O I]145/L-IR, and [C II]/L-IR ratios compared to lower luminosity systems. The majority of the line deficits are consistent with dustier H II regions, but part of the [C II] deficit may arise from an additional mechanism, plausibly charged dust grains. This is consistent with some of the [C II] originating from photodissociation regions or the interstellar medium (ISM). We derive relations between far-IR line luminosities and both the IR luminosity and star formation rate. We find that [N II] and both [O I] lines are good tracers of the IR luminosity and star formation rate. In contrast, [C II] is a poor tracer of the IR luminosity and star formation rate, and does not improve as a tracer of either quantity if the [C II] deficit is accounted for. The continuum luminosity densities also correlate with the IR luminosity and star formation rate. We derive ranges for the gas density and ultraviolet radiation intensity of 10(1) < n < 10(2.5) and 10(2.2) < G(0) < 10(3.6), respectively. These ranges depend on optical type, the importance of star formation, and merger stage. We do not find relationships between far-IR line properties and several other parameters: active galactic nucleus (AGN) activity, merger stage, mid-IR excitation, and SMBH mass. We conclude that these far-IR lines arise from gas heated by starlight, and that they are not strongly influenced by AGN activity.