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Evidence for a Clumpy, Rotating Gas Disk in a Submillimeter Galaxy at z = 4

Hodge, J. A. and Carilli, C. L. and Walter, F. and de Blok, W. J. G. and Riechers, D. and Daddi, E. and Lentati, L. (2012) Evidence for a Clumpy, Rotating Gas Disk in a Submillimeter Galaxy at z = 4. Astrophysical Journal, 760 (1). Art. No. 11. ISSN 0004-637X. doi:10.1088/0004-637X/760/1/11. https://resolver.caltech.edu/CaltechAUTHORS:20121218-085329697

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Abstract

We present Karl G. Jansky Very Large Array observations of the CO(2-1) emission in the z = 4.05 submillimeter galaxy (SMG) GN20. These high-resolution data allow us to image the molecular gas at 1.3 kpc resolution just 1.6 Gyr after the big bang. The data reveal a clumpy, extended gas reservoir, 14 ± 4 kpc in diameter, in unprecedented detail. A dynamical analysis shows that the data are consistent with a rotating disk of total dynamical mass 5.4 ± 2.4 × 10^(11) M_☉. We use this dynamical mass estimate to constrain the CO-to-H_2 mass conversion factor (α_(CO)), finding α_(CO) = 1.1 ± 0.6 M ☉(K km s^(–1) pc^2)^(–1). We identify five distinct molecular gas clumps in the disk of GN20 with masses a few percent of the total gas mass, brightness temperatures of 16-31K, and surface densities of >3200-4500 × (α_(CO)/0.8) M_☉ pc^(–2). Virial mass estimates indicate they could be self-gravitating, and we constrain their CO-to-H_2 mass conversion factor to be <0.2-0.7 M_☉(K km s^(–1) pc^2)^(–1). A multiwavelength comparison demonstrates that the molecular gas is concentrated in a region of the galaxy that is heavily obscured in the rest-frame UV/optical. We investigate the spatially resolved gas excitation and find that the CO(6-5)/CO(2-1) ratio is constant with radius, consistent with star formation occurring over a large portion of the disk. We discuss the implications of our results in the context of different fueling scenarios for SMGs.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/760/1/11DOIArticle
http://iopscience.iop.org/0004-637X/760/1/11PublisherArticle
ORCID:
AuthorORCID
Hodge, J. A.0000-0001-6586-8845
Carilli, C. L.0000-0001-6647-3861
Walter, F.0000-0003-4793-7880
Riechers, D.0000-0001-9585-1462
Daddi, E.0000-0002-3331-9590
Additional Information:© 2012 American Astronomical Society. Received 2011 December 22; accepted 2012 September 11; published 2012 October 30. The authors thank the anonymous referee for helpful comments which improved this paper. We thank Glenn Morrison, Mark Dickinson, Bram Venemans, Gabriel Brammer, Desika Narayanan, Benjamin Weiner, and Dario Colombo for useful comments and discussions. C.C. thanks the Kavli institute of Cosmology for their hospitality. D.R. acknowledges funding from NASA through a Spitzer Space Telescope grant. The National Radio Astronomy Observatory is a facility of the National Science Foundation under cooperative agreement by Associated Universities, Inc. This research has made use of the GIPSY package.
Funders:
Funding AgencyGrant Number
NASA Spitzer Space TelescopeUNSPECIFIED
Subject Keywords:galaxies: evolution; galaxies: formation; galaxies: high-redshift; galaxies: ISM; galaxies: star formation
Issue or Number:1
DOI:10.1088/0004-637X/760/1/11
Record Number:CaltechAUTHORS:20121218-085329697
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20121218-085329697
Official Citation:Evidence for a Clumpy, Rotating Gas Disk in a Submillimeter Galaxy at z = 4 J. A. Hodge, C. L. Carilli, F. Walter, W. J. G. de Blok, D. Riechers, E. Daddi, and L. Lentati doi:10.1088/0004-637X/760/1/11
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36025
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:18 Dec 2012 17:09
Last Modified:09 Nov 2021 23:19

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