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  • A Herschel Space Observator...
    Lu, Nanyao; Zhao, Yinghe; Díaz-Santos, Tanio; Xu, C. Kevin; Gao, Yu; Armus, Lee; Isaak, Kate G.; Mazzarella, Joseph M.; van der Werf, Paul P.; Appleton, Philip N.; Charmandaris, Vassilis; Evans, Aaron S.; Howell, Justin; Iwasawa, Kazushi; Leech, Jamie; Lord, Steven; Petric, Andreea O.; Privon, George C.; Sanders, David B.; Schulz, Bernhard; Surace, Jason A.

    The Astrophysical journal. Supplement series, 05/2017, Letnik: 230, Številka: 1
    Journal Article

    Abstract We describe a Herschel Space Observatory 194–671 μ m spectroscopic survey of a sample of 121 local luminous infrared galaxies and report the fluxes of the CO J to J –1 rotational transitions for , the N ii 205 μ m line, the C i lines at 609 and 370 μ m, as well as additional and usually fainter lines. The CO spectral line energy distributions (SLEDs) presented here are consistent with our earlier work, which was based on a smaller sample, that calls for two distinct molecular gas components in general: (i) a cold component, which emits CO lines primarily at J  ≲ 4 and likely represents the same gas phase traced by CO (1−0), and (ii) a warm component, which dominates over the mid- J regime (4 <  J  ≲ 10) and is intimately related to current star formation. We present evidence that the CO line emission associated with an active galactic nucleus is significant only at J  > 10. The flux ratios of the two C i lines imply modest excitation temperatures of 15–30 K; the C i 370 μ m line scales more linearly in flux with CO (4−3) than with CO (7−6). These findings suggest that the C i emission is predominantly associated with the gas component defined in (i) above. Our analysis of the stacked spectra in different far-infrared (FIR) color bins reveals an evolution of the SLED of the rotational transitions of vapor as a function of the FIR color in a direction consistent with infrared photon pumping.