FAR-INFRARED FINE-STRUCTURE LINE DIAGNOSTICS OF ULTRALUMINOUS INFRARED GALAXIES
- Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States)
- Cornell University, CRSR, Space Sciences Building, Ithaca, NY 14853 (United States)
- Department of Physics and Astronomy, The Open University, Milton Keynes MK7 6AA (United Kingdom)
- RAL Space, Rutherford Appleton Laboratory, Harwell, Oxford OX11 0QX (United Kingdom)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Universidad de Alcalá, Departamento de Física y Matemáticas, Campus Universitario, E-28871 Alcalá de Henares, Madrid (Spain)
- Physics Department, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom)
- School of Sciences, European University Cyprus, Diogenes Street, Engomi, 1516 Nicosia (Cyprus)
- Institut für theoretische Astrophysik, Zentrum für Astronomie der Universität Heidelberg, Albert-Ueberle Str. 2, D-69120 Heidelberg (Germany)
- Centro de Astronomia e Astrofísica da Universidade de Lisboa, Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisbon (Portugal)
- Department of Physics and Astronomy, University of Sussex, Falmer, Brighton BN1 9QH (United Kingdom)
- Infrared Processing and Analysis Center, MS220-6, California Institute of Technology, Pasadena, CA 91125 (United States)
- Oxford Astrophysics, Denys Wilkinson Building, University of Oxford, Keble Rd, Oxford OX1 3RH (United Kingdom)
- Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)
We present Herschel observations of 6 fine-structure lines in 25 ultraluminous infrared galaxies at z < 0.27. The lines, [O III]52 μm, [N III]57 μm, [O I]63 μm, [N II]122 μm, [O I]145 μm, and [C II]158 μm, are mostly single Gaussians with widths <600 km s{sup –1} and luminosities of 10{sup 7}-10{sup 9} L{sub ☉}. There are deficits in the [O I]63/L{sub IR}, [N II]/L{sub IR}, [O I]145/L{sub IR}, and [C II]/L{sub 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{sup 1} < n < 10{sup 2.5} and 10{sup 2.2} < G{sub 0} < 10{sup 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.
- OSTI ID:
- 22270722
- Journal Information:
- Astrophysical Journal, Vol. 776, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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