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GOODS-Herschel: Gas-to-dust Mass Ratios and CO-to-H_2 Conversion Factors in Normal and Starbursting Galaxies at High-z

Magdis, Georgios E. and Daddi, E. and Elbaz, D. and Sargent, M. T. and Dickinson, M. and Dannerbauer, H. and Aussel, H. and Walter, F. and Hwang, H. S. and Charmandaris, V. and Hodge, J. and Riechers, D. and Rigopoulou, D. and Carilli, C. and Pannella, M. and Mullaney, J. and Leiton, R. and Scott, D. (2011) GOODS-Herschel: Gas-to-dust Mass Ratios and CO-to-H_2 Conversion Factors in Normal and Starbursting Galaxies at High-z. Astrophysical Journal Letters, 740 (1). Art. No. L15. ISSN 2041-8205.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Magdis, Georgios E.0000-0002-4872-2294
Daddi, E.0000-0002-3331-9590
Elbaz, D.0000-0002-7631-647X
Sargent, M. T.0000-0003-1033-9684
Dickinson, M.0000-0001-5414-5131
Dannerbauer, H.0000-0001-7147-3575
Aussel, H.0000-0002-1371-5705
Walter, F.0000-0003-4793-7880
Charmandaris, V.0000-0002-2688-1956
Hodge, J.0000-0001-6586-8845
Riechers, D.0000-0001-9585-1462
Rigopoulou, D.0000-0001-6854-7545
Carilli, C.0000-0001-6647-3861
Mullaney, J.0000-0002-3126-6712
Scott, D.0000-0002-6878-9840
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.
Funding AgencyGrant Number
Oxford UniversityUNSPECIFIED
European Research Council (ERC)UPGAL-240039
Agence Nationale pour la Recherche (ANR)ANR-08-JCJC- 0008
Subject Keywords:galaxies: evolution; galaxies: high-redshift; galaxies: starburst; galaxies: star formation; infrared: galaxies
Issue or Number:1
Classification Code:PACS: 98.54.Ep; 98.62.Ai; 98.62.Bj; 98.62.Ck
Record Number:CaltechAUTHORS:20111017-113343110
Persistent URL:
Official Citation:GOODS-Herschel: Gas-to-dust Mass Ratios and CO-to-H2 Conversion Factors in Normal and Starbursting Galaxies at High-z Georgios E. Magdis et al. 2011 ApJ 740 L15
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:27256
Deposited By: Ruth Sustaita
Deposited On:18 Oct 2011 14:48
Last Modified:09 Mar 2020 13:19

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