@article{9ae26f7d48f7497d8a8900104e4f517e,
title = "A Herschel/PACS Far-infrared Line Emission Survey of Local Luminous Infrared Galaxies",
abstract = "We present an analysis of [O I]63, [O III]88, [N II]122, and [C II]158 far-infrared (FIR) fine-structure line observations obtained with Herschel/PACS, for ∼240 local luminous infrared galaxies (LIRGs) in the Great Observatories Allsky LIRG Survey. We find pronounced declines ({"}deficits{"}) of line-to-FIR continuum emission for [N II]122, [O I]63, and [C II]158 as a function of FIR color and infrared luminosity surface density, IR. The median electron density of the ionized gas in LIRGs, based on the [N II]122/[N II]205 ratio, is ne=41 cm-3. We find that the dispersion in the [C II]158 deficit of LIRGs is attributed to a varying fractional contribution of photodissociation regions (PDRs) to the observed [C II]158 emission, f ([C II]158PDR)=[C II]158PDR/[C II]158, which increases from ∼60% to ∼95% in the warmest LIRGs. The [O I]63/[C II]158PDR ratio is tightly correlated with the PDR gas kinetic temperature in sources where [O I]63 is not optically thick or self-absorbed. For each galaxy, we derive the average PDR hydrogen density, nH, and intensity of the interstellar radiation field, G, in units of G0 and find G/nH ratios of ∼0.1-50G0cm3, with ULIRGs populating the upper end of the distribution. There is a relation between G/nH and IR, showing a critical break at IR∗; 5 × 1010 L kpc-2. BelowIR∗, G/nH remains constant, ;0.32G0cm3, and variations inIR are driven by the number density of star-forming regions within a galaxy, with no change in their PDR properties. AboveIR∗, G/nH increases rapidly withIR, signaling a departure from the typical PDR conditions found in normal star-forming galaxies toward more intense/harder radiation fields and compact geometries typical of starbursting sources.",
keywords = "galaxies: ISM, galaxies: evolution, galaxies: nuclei, galaxies: starburst, infrared: galaxies",
author = "T. D{\'i}az-Santos and L. Armus and V. Charmandaris and N. Lu and S. Stierwalt and G. Stacey and S. Malhotra and Werf, {P. P.Van Der} and Howell, {J. H.} and Privon, {G. C.} and Mazzarella, {J. M.} and Goldsmith, {P. F.} and Murphy, {E. J.} and L. Barcos-Mu{\~n}oz and Linden, {S. T.} and H. Inami and Larson, {K. L.} and Evans, {A. S.} and P. Appleton and K. Iwasawa and S. Lord and Sanders, {D. B.} and Surace, {J. A.}",
note = "Funding Information: We thank the referee for her/his useful comments. T.D.-S. would like to thank M. Wolfire, J. Pineda, C. Ferkinhoff, D. Brisbin, and N. Scoville for stimulating discussions about PDR physics and models. T.D.-S. acknowledges support from ALMA-CONICYT project 31130005 and FONDECYT regular project 1151239. G.C.P. was supported by a FONDECYT Postdoctoral Fellowship (no. 3150361). N.L. acknowledges support from NSFC grant no. 11673028. K.I. acknowledges support by the Spanish MINECO under grant AYA2016-76012-C3-1-P and MDM-2014-0369 of ICCUB (Unidad de Excelencia “Mar{\'i}a de Maeztu”). This work was carried out in part at the Jet Propulsion Laboratory, which is operated for NASA by the California Institute of Technology. This work is based on observations made with the Herschel Space Observatory, a European Space Agency Cornerstone Mission with science instruments provided by European-led Principal Investigator consortia and significant participation from NASA. The Spitzer Space Telescope is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, and of NASA{\textquoteright}s Astrophysics Data System (ADS) abstract service. T.D.-S. wants to thank the NASA Herschel Science Center (NHSC), and in particular D. Shupe, for providing access to their computer cluster, with which most of the Herschel/PACS data sets were processed. Part of this work was carried out at the Aspen Center for Physics, which is supported by the National Science Foundation grant PHY-1066293. Publisher Copyright: {\textcopyright} 2017. The American Astronomical Society. All rights reserved.",
year = "2017",
month = sep,
day = "1",
doi = "10.3847/1538-4357/aa81d7",
language = "English (US)",
volume = "846",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1",
}