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Molecular Gas Reservoirs of z ∼ 2 Galaxies: A Comparison of CO(1−0) and Dust-based Molecular Gas Masses

Kaasinen, M. and Scoville, N. and Walter, F. and da Cunha, E. and Popping, G. and Pavesi, R. and Darvish, B. and Casey, C. M. and Riechers, D. A. and Glover, S. (2019) Molecular Gas Reservoirs of z ∼ 2 Galaxies: A Comparison of CO(1−0) and Dust-based Molecular Gas Masses. Astrophysical Journal, 880 (1). Art. No. 15. ISSN 1538-4357.

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We test the use of long-wavelength dust continuum emission as a molecular gas tracer at high redshift, via a unique sample of a dozen z ~ 2 galaxies with observations of both the dust continuum and CO(1−0) line emission (obtained with the Atacama Large Millimeter Array and Karl G. Jansky Very Large Array, respectively). Our work is motivated by recent high-redshift studies that measure molecular gas masses (M_(mol)) via a calibration of the rest-frame 850 μm luminosity (L_(850 μm,rest)) against the CO(1−0)-derived M_(mol) of star-forming galaxies. We therefore test whether this method is valid for the types of high-redshift, star-forming galaxies to which it has been applied. We recover a clear correlation between the rest-frame 850 μm luminosity, inferred from the single-band, long-wavelength flux, and the CO(1−0) line luminosity, consistent with the samples used to perform the 850 μm calibration. The molecular gas masses, derived from L_(850 μm,rest), agree to within a factor of two with those derived from CO(1−0). We show that this factor of two uncertainty can arise from the values of the dust emissivity index and temperature that need to be assumed in order to extrapolate from the observed frequency to the rest-frame at 850 μm. The extrapolation to 850 μm therefore has a smaller effect on the accuracy of M_(mol) derived via single-band dust-continuum observations than the assumed CO(1−0)-to- M_(mol) conversion factor. We therefore conclude that single-band observations of long-wavelength dust emission can be used to reliably constrain the molecular gas masses of massive, star-forming galaxies at z ≳ 2.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kaasinen, M.0000-0002-1173-2579
Scoville, N.0000-0002-0438-3323
Walter, F.0000-0003-4793-7880
da Cunha, E.0000-0001-9759-4797
Popping, G.0000-0003-1151-4659
Pavesi, R.0000-0002-2263-646X
Darvish, B.0000-0003-4919-9017
Casey, C. M.0000-0002-0930-6466
Riechers, D. A.0000-0001-9585-1462
Additional Information:© 2019 The American Astronomical Society. Received 2018 November 17; revised 2019 May 1; accepted 2019 May 26; published 2019 July 18. We thank the anonymous referee, whose comments improved the clarity and details of this work. We also thank Olivier Ilbert for the assistance provided in cross-checking the fits to the COSMOS photometry using LePHARE. We further extend our gratitude to Alberto Bolatto and Desika Narayanan for their helpful insights. S.C.O.G. acknowledges support from the DFG via SFB 881 "The Milky Way System" (sub-projects B1, B2, and B8). C.M.C. thanks UT Austin College of Natural Sciences for support in addition to support from NSF grants AST-1714528 and AST-1814034. B.D. acknowledges financial support from the National Science Foundation, grant No. 1716907. D.R. and R.P. acknowledge support from the NSF, through grant AST-1614213. E.dC., as the recipient of a Future Fellowship (project FT150100079), gratefully acknowledges the Australian Research Council. M.K. acknowledges support from the International Max Planck Research School for Astronomy and Cosmic Physics at Heidelberg University (IMPRS-HD). Parts of this research were conducted by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. This paper makes use of VLA data VLA/17A-251, as well as ALMA data 2013.1.00034.S, 2015.1.00137.S, 2013.1.00118.S, and 2013.1.00151.S. 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 near-IR spectroscopy presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors would like to recognize and acknowledge the very prominent cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are fortunate to have the opportunity to perform observations from this mountain. Facilities: VLA - Very Large Array, ALMA - , Keck I. -
Group:Astronomy Department
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)SFB 881
University of Texas at AustinUNSPECIFIED
Australian Research CouncilFT150100079
Heidelberg UniversityUNSPECIFIED
Australian Research CouncilCE170100013
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:galaxies: high-redshift – galaxies: ISM
Issue or Number:1
Record Number:CaltechAUTHORS:20190718-124406342
Persistent URL:
Official Citation:M. Kaasinen et al 2019 ApJ 880 15
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97232
Deposited By: Tony Diaz
Deposited On:18 Jul 2019 21:07
Last Modified:09 Mar 2020 13:19

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