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The Rest-frame Submillimeter Spectrum of High-redshift, Dusty, Star-forming Galaxies

Spilker, J. S. and Vieira, J. D. (2014) The Rest-frame Submillimeter Spectrum of High-redshift, Dusty, Star-forming Galaxies. Astrophysical Journal, 785 (2). Art. No. 149. ISSN 0004-637X.

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We present the average rest-frame spectrum of high-redshift dusty, star-forming galaxies from 250 to 770 GHz. This spectrum was constructed by stacking Atacama Large Millimeter/submillimeter Array (ALMA) 3 mm spectra of 22 such sources discovered by the South Pole Telescope and spanning z = 2.0-5.7. In addition to multiple bright spectral features of ^(12)CO, [C I], and H_2O, we also detect several faint transitions of ^(13)CO, HCN, HNC, HCO^+, and CN, and use the observed line strengths to characterize the typical properties of the interstellar medium of these high-redshift starburst galaxies. We find that the ^(13)CO brightness in these objects is comparable to that of the only other z > 2 star-forming galaxy in which ^(13)CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO^+, and CN is consistent with a warm, dense medium with T_(kin) ~ 55 K and n_H_2 ≳ 10^(5.5) cm^(–3). High molecular hydrogen densities are required to reproduce the observed line ratios, and we demonstrate that alternatives to purely collisional excitation are unlikely to be significant for the bulk of these systems. We quantify the average emission from several species with no individually detected transitions, and find emission from the hydride CH and the linear molecule CCH for the first time at high redshift, indicating that these molecules may be powerful probes of interstellar chemistry in high-redshift systems. These observations represent the first constraints on many molecular species with rest-frame transitions from 0.4 to 1.2 mm in star-forming systems at high redshift, and will be invaluable in making effective use of ALMA in full science operations.

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Additional Information:© 2014 American Astronomical Society. Received 2013 October 31; accepted 2014 March 6; published 2014 April 4. This material is based on work supported by the U.S. National Science Foundation under grant No. AST-1312950. The SPT is supported by the National Science Foundation through grant ANT-0638937, with partial support through PHY-1125897, the Kavli Foundation and the Gordon and Betty Moore Foundation. This paper makes use of the following ALMA data: ADS/JAO.ALMA2011.0.00957.S and 2011.0.00958.S.ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The Australia Telescope Compact Array is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. This research has made use of NASA’s Astrophysics Data System.
Funding AgencyGrant Number
Kavli FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Commonwealth of AustraliaUNSPECIFIED
Subject Keywords:galaxies: high-redshift; galaxies: ISM; galaxies: star formation; ISM: molecules
Issue or Number:2
Record Number:CaltechAUTHORS:20140618-132405742
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Official Citation:The Rest-frame Submillimeter Spectrum of High-redshift, Dusty, Star-forming Galaxies J. S. Spilker et al. 2014 ApJ 785 149
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46339
Deposited By: Ruth Sustaita
Deposited On:18 Jun 2014 21:09
Last Modified:03 Oct 2019 06:43

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