Stacked average far-infrared spectrum of dusty star-forming galaxies from the Herschel/SPIRE Fourier Transform Spectrometer

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Title: Stacked average far-infrared spectrum of dusty star-forming galaxies from the Herschel/SPIRE Fourier Transform Spectrometer
Authors: Wilson, D
Cooray, A
Nayyeri, H
Bonato, M
Bradford, CM
Clements, DL
De Zotti, G
Diaz-Santos, T
Farrah, D
Magdis, G
Michalowski, MJ
Pearson, C
Rigopoulou, D
Valtchanov, I
Wang, L
Wardlow, J
Item Type: Journal Article
Abstract: We present stacked average far-infrared spectra of a sample of 197 dusty star-forming galaxies (DSFGs) at $0.005\lt z\lt 4$ 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 H2O rotational transitions and consider PDR conditions based on observed [C i] 370 and 609 μm, and CO (7-6) lines. For the high-z ($0.8\lt z\lt 4$) sample, PDR models suggest a molecular gas distribution in the presence of a radiation field that is at least a factor of 103 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.
Issue Date: 10-Oct-2017
Date of Acceptance: 12-Sep-2017
ISSN: 0004-637X
Publisher: American Astronomical Society
Journal / Book Title: Astrophysical Journal
Volume: 848
Issue: 1
Copyright Statement: © 2017 The American Astronomical Society. All rights reserved.
Keywords: Science & Technology
Physical Sciences
Astronomy & Astrophysics
galaxies: high-redshift
galaxies: ISM
ISM: general
APM 08279+5255
0201 Astronomical And Space Sciences
0305 Organic Chemistry
0306 Physical Chemistry (Incl. Structural)
Publication Status: Published
Article Number: 30
Online Publication Date: 2017-10-09
Appears in Collections:Physics

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