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Stacked Average Far-infrared Spectrum of Dusty Star-forming Galaxies from the Herschel/SPIRE Fourier Transform Spectrometer

Wilson, Derek and Cooray, Asantha and Nayyeri, Hooshang and Bonato, Matteo and Bradford, Charles M. and Clements, David L. and De Zotti, Gianfranco and Díaz-Santos, Tanio and Farrah, Duncan and Magdis, Georgios and Michałowski, Michał J. and Pearson, Chris and Rigopoulou, Dimitra and Valtchanov, Ivan and Wang, Lingyu and Wardlow, Julie (2017) Stacked Average Far-infrared Spectrum of Dusty Star-forming Galaxies from the Herschel/SPIRE Fourier Transform Spectrometer. Astrophysical Journal, 848 (1). Art. No. 30. ISSN 1538-4357.

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We present stacked average far-infrared spectra of a sample of 197 dusty star-forming galaxies (DSFGs) at 0.005 < z < 4 using about 90% of the Herschel Space Observatory SPIRE Fourier Transform Spectrometer (FTS) extragalactic data archive based on 3.5 years of science operations. These spectra explore an observed-frame 447–1568 GHz frequency range, allowing us to observe the main atomic and molecular lines emitted by gas in the interstellar medium. The sample is subdivided into redshift bins, and a subset of the bins are stacked by infrared luminosity as well. These stacked spectra are used to determine the average gas density and radiation field strength in the photodissociation regions (PDRs) of DSFGs. For the low-redshift sample, we present the average spectral line energy distributions of CO and H_2O rotational transitions and consider PDR conditions based on observed [C I] 370 and 609 μm, and CO (7-6) lines. For the high-z (0.8 < z < 4) sample, PDR models suggest a molecular gas distribution in the presence of a radiation field that is at least a factor of 10^3 larger than the Milky Way and with a neutral gas density of roughly 10^(4.5)-10^(5.5) cm^(−3). The corresponding PDR models for the low-z sample suggest a UV radiation field and gas density comparable to those at high-z. Given the challenges in obtaining adequate far-infrared observations, the stacked average spectra we present here will remain the measurements with the highest signal-to-noise ratio for at least a decade and a half until the launch of the next far-infrared facility.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Wilson, Derek0000-0001-6002-423X
Cooray, Asantha0000-0002-3892-0190
Nayyeri, Hooshang0000-0001-8242-9983
Clements, David L.0000-0002-9548-5033
De Zotti, Gianfranco0000-0003-2868-2595
Díaz-Santos, Tanio0000-0003-0699-6083
Farrah, Duncan0000-0003-1748-2010
Magdis, Georgios0000-0002-4872-2294
Pearson, Chris0000-0001-6139-649X
Valtchanov, Ivan0000-0001-9930-7886
Wardlow, Julie0000-0003-2376-8971
Additional Information:© 2017 The American Astronomical Society. Received 2017 May 1; revised 2017 September 1; accepted 2017 September 12; published 2017 October 9. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. The authors thank the anonymous referee for the helpful comments and suggestions. The authors also thank Rodrigo Herrera-Camus, Eckhard Sturm, Javier Gracia-Carpio, and SHINING for sharing a compilation of [C ii], [O iii], and [O i] line measurements as well as FIR data to which we compare our results. We wish to thank Paul Van der Werf for the very useful suggestions and recommendations. Support for this paper was provided in part by NSF grant AST-1313319, NASA grant NNX16AF38G, GAANN P200A150121, HST-GO-13718, HST-GO-14083, and NSF Award #1633631. J.L.W. is supported by a European Union COFUND/Durham Junior Research Fellowship under EU grant agreement number 609412, and acknowledges additional support from STFC (ST/L00075X/1). G.D.Z. acknowledges support from the ASI/INAF agreement n. 2014-024-R.1. The Herschel spacecraft was designed, built, tested, and launched under a contract to ESA managed by the Herschel/Planck Project team by an industrial consortium under the overall responsibility of the prime contractor Thales Alenia Space (Cannes), and including Astrium (Friedrichshafen) responsible for the payload module and for system testing at spacecraft level, Thales Alenia Space (Turin) responsible for the service module, and Astrium (Toulouse) responsible for the telescope, with in excess of a hundred subcontractors. SPIRE has been developed by a consortium of institutes led by Cardiff University (UK) and including Univ. Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, Univ. Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, Univ. Sussex (UK); and Caltech, JPL, NHSC, Univ. Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC, UKSA (UK); and NASA (USA). HIPE is a joint development by the Herschel Science Ground Segment Consortium, consisting of ESA, the NASA Herschel Science Center, and the HIFI, PACS, and SPIRE consortia. 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.
Funding AgencyGrant Number
NASA Hubble FellowshipHST-GO-13718
NASA Hubble FellowshipHST-GO-14083
European Research Council (ERC)609412
Science and Technology Facilities Council (STFC)ST/L00075X/1
Agenzia Spaziale Italiana (ASI)2014-024-R.1
Subject Keywords:galaxies: high-redshift – galaxies: ISM – ISM: general
Record Number:CaltechAUTHORS:20171009-152948437
Persistent URL:
Official Citation:Derek Wilson et al 2017 ApJ 848 30
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82234
Deposited By: Tony Diaz
Deposited On:09 Oct 2017 22:52
Last Modified:24 Oct 2017 23:10

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