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

Wardlow, Julie L. and Cooray, Asantha and Osage, Willow and Bourne, Nathan and Clements, David and Dannerbauer, Helmut and Dunne, Loretta and Dye, Simon and Eales, Steve and Farrah, Duncan and Furlanetto, Cristina and Ibar, Edo and Ivison, Rob and Maddox, Steve and Michałowski, Michał M. and Riechers, Dominik and Rigopoulou, Dimitra and Scott, Douglas and Smith, Matthew W. L. and Wang, Lingyu and van der Werf, Paul and Valiante, Elisabetta and Valtchanov, Ivan and Verma, Aprajita (2017) The Interstellar Medium in High-redshift Submillimeter Galaxies as Probed by Infrared Spectroscopy*. The Astrophysical Journal, 837 (1). ISSN 0004-637X

[img]
Preview
PDF (1701.03112)
1701.03112.pdf - Accepted Version
Available under License Creative Commons Attribution-NonCommercial.

Download (2MB)

Abstract

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.

Item Type:
Journal Article
Journal or Publication Title:
The Astrophysical Journal
Additional Information:
© 2017. The American Astronomical Society. All rights reserved.
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/1900/1912
Subjects:
ID Code:
128221
Deposited By:
Deposited On:
22 Oct 2018 11:10
Refereed?:
Yes
Published?:
Published
Last Modified:
20 Sep 2020 05:08