GOODS-Herschel: Gas-to-dust Mass Ratios and CO-to-H_2 Conversion Factors in Normal and Starbursting Galaxies at High-z
Creators
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1.
University of Oxford
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NOIRLab
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3.
Max Planck Institute for Astronomy
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University of Crete
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Foundation for Research and Technology Hellas
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Paris Observatory
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7.
California Institute of Technology
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8.
National Radio Astronomy Observatory
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University of British Columbia
Abstract
We explore the gas-to-dust mass ratio (M_gas/M_d) and the CO luminosity-to-M_gas conversion factor (α_(CO)) of two well-studied galaxies in the Great Observatories Origins Deep Survey North field that are expected to have different star-forming modes, the starburst GN20 at z = 4.05 and the normal star-forming galaxy BzK-21000 at z = 1.52. Detailed sampling is available for their Rayleigh-Jeans emission via ground-based millimeter (mm) interferometry (1.1-6.6 mm) along with Herschel PACS and SPIRE data that probe the peak of their infrared emission. Using the physically motivated Draine & Li models, as well as a modified blackbody function, we measure the dust mass (M_(dust)) of the sources and find (2.0^(+0.7)_(–0.6) × 10^9) M_☉for GN20 and (8.6^(+0.6)_(–0.9) × 10^8) M_☉ for BzK-21000. The addition of mm data reduces the uncertainties of the derived M_(dust) by a factor of ~2, allowing the use of the local M_(gas)/M_d versus metallicity relation to place constraints on the αCO values of the two sources. For GN20 we derive a conversion factor of α_(CO) < 1.0 M_☉ pc^(–2) (K km s^(–1))^(–1), consistent with that of local ultra-luminous infrared galaxies, while for BzK-21000 we find a considerably higher value, α_(CO) ~4.0 M_☉ pc^(–2) (K km s^(–1))^(–1), in agreement with an independent kinematic derivation reported previously. The implied star formation efficiency is ~25 L_☉/M_☉ for BzK-21000, a factor of ~5-10 lower than that of GN20. The findings for these two sources support the existence of different disk-like and starburst star formation modes in distant galaxies, although a larger sample is required to draw statistically robust results.
Additional Information
© 2011 The American Astronomical Society. Received 2011 July 17; accepted 2011 August 26; published 2011 September 20. We thank Alvio Renzini for useful discussions. G.E.M. acknowledges support from Oxford University. E.D. acknowledges funding support from ERC-StG grant UPGAL240039 and ANR-08-JCJC- 0008. D.R. acknowledges support from NASA through a Spitzer Space Telescope grant. This work is based on observations made with the Herschel Space Observatory, a European Space Agency Cornerstone Mission with significant participation by NASA.Attached Files
Published - Magdis2011p16042Astrophys_J_Lett.pdf
Files
Magdis2011p16042Astrophys_J_Lett.pdf
Additional details
Identifiers
- Eprint ID
- 27256
- Resolver ID
- CaltechAUTHORS:20111017-113343110
Funding
- Oxford University
- European Research Council (ERC)
- UPGAL-240039
- Agence Nationale pour la Recherche (ANR)
- ANR-08-JCJC- 0008
- NASA
Dates
- Created
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2011-10-18Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field
Caltech Custom Metadata
- Caltech groups
- Physics Department