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  • 1701.03112

    Rights statement: © 2017. The American Astronomical Society. All rights reserved.

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The Interstellar Medium in High-redshift Submillimeter Galaxies as Probed by Infrared Spectroscopy*

Research output: Contribution to journalJournal articlepeer-review

  • Asantha Cooray
  • Willow Osage
  • Nathan Bourne
  • David Clements
  • Helmut Dannerbauer
  • Loretta Dunne
  • Simon Dye
  • Steve Eales
  • Duncan Farrah
  • Cristina Furlanetto
  • Edo Ibar
  • Rob Ivison
  • Steve Maddox
  • Michał M. Michałowski
  • Dominik Riechers
  • Dimitra Rigopoulou
  • Douglas Scott
  • Matthew W. L. Smith
  • Lingyu Wang
  • Paul van der Werf
  • Elisabetta Valiante
  • Ivan Valtchanov
  • Aprajita Verma
Article number12
<mark>Journal publication date</mark>1/03/2017
<mark>Journal</mark>The Astrophysical Journal
Issue number1
Number of pages20
Publication StatusPublished
Early online date27/02/17
<mark>Original language</mark>English


Submillimeter galaxies (SMGs) at z≳ 1 are luminous in the far-infrared, and have star formation rates, SFR, of hundreds to thousands of solar masses per year. However, it is unclear whether they are true analogs of local ULIRGs or whether the mode of their star formation is more similar to that in local disk galaxies. We target these questions by using Herschel-PACS to examine the conditions in the interstellar medium (ISM) in far-infrared luminous SMGs at z˜ 1-4. We present 70-160 μm photometry and spectroscopy of the [O IV]26 μm, [Fe II]26 μm, [S III]33 μm, [Si II]34 μm, [O III]52 μm, [N III]57 μm, and [O I]63 μm fine-structure lines and the S(0) and S(1) hydrogen rotational lines in 13 lensed SMGs identified by their brightness in early Herschel data. Most of the 13 targets are not individually spectroscopically detected; we instead focus on stacking these spectra with observations of an additional 32 SMGs from the Herschel archive—representing a complete compilation of PACS spectroscopy of SMGs. We detect [O I]63 μm, [Si II]34 μm, and [N III]57 μm at ≥slant 3σ in the stacked spectra, determining that the average strengths of these lines relative to the far-IR continuum are (0.36+/- 0.12)× {10}-3, (0.84+/- 0.17)× {10}-3, and (0.27+/- 0.10)× {10}-3, respectively. Using the [O III]52 μm/[N III]57 μm emission line ratio, we show that SMGs have average gas-phase metallicities ≳ {Z}⊙ . By using PDR modeling and combining the new spectral measurements with integrated far-infrared fluxes and existing [C II]158 μm data, we show that SMGs have average gas densities, n, of ˜ {10}1-3 {{cm}}-3 and FUV field strengths, {G}0˜ {10}2.2-4.5 (in Habing units: 1.6× {10}-3 {erg} {{cm}}-2 {{{s}}}-1), consistent with both local ULIRGs and lower luminosity star-forming galaxies. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia, and important participation from NASA.

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© 2017. The American Astronomical Society. All rights reserved.