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A Herschel/PACS Far-infrared Line Emission Survey of Local Luminous Infrared Galaxies

Díaz-Santos, T. and Armus, L. and Charmandaris, V. and Lu, N. and Stierwalt, S. and Stacey, G. and Malhotra, S. and van der Werf, P. P. and Howell, J. H. and Privon, G. C. and Mazzarella, J. M. and Goldsmith, P. F. and Murphy, E. J. and Barcos-Muñoz, L. and Linden, S. T. and Inami, H. and Larson, K. L. and Evans, A. S. and Appleton, P. and Iwasawa, K. and Lord, S. and Sanders, D. B. and Surace, J. A. (2017) A Herschel/PACS Far-infrared Line Emission Survey of Local Luminous Infrared Galaxies. Astrophysical Journal, 846 (1). Art. No. 32. ISSN 1538-4357. doi:10.3847/1538-4357/aa81d7.

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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 All-sky 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, Σ_(IR). The median electron density of the ionized gas in LIRGs, based on the [N II]_(122)/[N II]_(205) ratio, is n_e = 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]^(PDR)_(158)) = [C II]^(PDR)_(158)/[C II]_(158), which increases from ~60% to ~95% in the warmest LIRGs. The [O I]_(63)/[C II]^(PDR)_(158) ratio is tightly correlated with the PDR gas kinetic temperature in sources where [O 1]_(63) is not optically thick or self-absorbed. For each galaxy, we derive the average PDR hydrogen density, n_H, and intensity of the interstellar radiation field, G, in units of G_0 and find G/n_H ratios of ~0.1–50 G_0 cm^3, with ULIRGs populating the upper end of the distribution. There is a relation between G/n_H and Σ_(IR), showing a critical break at Σ*_(IR) 5 × 10^(10) L⊙ kpc^(−2). Below Σ*_(IR), G/n_H remains constant, 0.32 G_0 cm^3, and variations in Σ_(IR) are driven by the number density of star-forming regions within a galaxy, with no change in their PDR properties. Above Σ*_(IR), G/n_H increases rapidly with Σ_(IR), 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Díaz-Santos, T.0000-0003-0699-6083
Armus, L.0000-0003-3498-2973
Charmandaris, V.0000-0002-2688-1956
Lu, N.0000-0002-8948-1044
Stierwalt, S.0000-0002-2596-8531
Malhotra, S.0000-0002-9226-5350
van der Werf, P. P.0000-0001-5434-5942
Privon, G. C.0000-0003-3474-1125
Mazzarella, J. M.0000-0002-8204-8619
Goldsmith, P. F.0000-0002-6622-8396
Murphy, E. J.0000-0001-7089-7325
Barcos-Muñoz, L.0000-0003-0057-8892
Linden, S. T.0000-0002-1000-6081
Inami, H.0000-0003-4268-0393
Larson, K. L.0000-0003-3917-6460
Evans, A. S.0000-0003-2638-1334
Appleton, P.0000-0002-7607-8766
Iwasawa, K.0000-0002-4923-3281
Sanders, D. B.0000-0002-1233-9998
Surace, J. A.0000-0001-7291-0087
Additional Information:© 2017 The American Astronomical Society. Received 2017 February 9; revised 2017 July 16; accepted 2017 July 17; published 2017 August 29. 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 "María 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'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.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)31130005
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1151239
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)3150361
National Natural Science Foundation of China11673028
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2016-76012-C3-1-P
Ministerio de Economía, Industria y Competitividad (MINECO)MDM-2014-0369
Subject Keywords:galaxies: evolution – galaxies: ISM – galaxies: nuclei – galaxies: starburst – infrared: galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:20170830-091801185
Persistent URL:
Official Citation:T. Díaz-Santos et al 2017 ApJ 846 32
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:80950
Deposited By: Tony Diaz
Deposited On:30 Aug 2017 17:29
Last Modified:15 Nov 2021 19:39

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