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Dust Obscuration and Metallicity at High Redshift: New Inferences from UV, Hα, and 8 μm Observations of z ~ 2 Star-forming Galaxies

Reddy, Naveen A. and Erb, Dawn K. and Pettini, Max and Steidel, Charles C. and Shapley, Alice E. (2010) Dust Obscuration and Metallicity at High Redshift: New Inferences from UV, Hα, and 8 μm Observations of z ~ 2 Star-forming Galaxies. Astrophysical Journal, 712 (2). pp. 1070-1091. ISSN 0004-637X.

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We use a sample of 90 spectroscopically confirmed Lyman break galaxies with Hα measurements and Spitzer MIPS 24 μm observations to constrain the relationship between rest-frame 8 μm luminosity (L_8) and star formation rate (SFR) for L* galaxies at z ~ 2. We find a tight correlation with 0.24 dex scatter between L_8 and Hα luminosity/SFR for z ~ 2 galaxies with 10^(10) L_☉ ≲ L_(IR) ≲ 10^(12) L_☉. Employing this relationship with a larger sample of 392 galaxies with spectroscopic redshifts, we find that the UV slope β can be used to recover the dust attenuation of the vast majority of moderately luminous L* galaxies at z ~ 2 to within a 0.4 dex scatter using the local correlation. Separately, young galaxies with ages ≲100 Myr appear to be less dusty than their UV slopes would imply based on the local trend and may follow an extinction curve that is steeper than what is typically assumed. Consequently, very young galaxies at high redshift may be significantly less dusty than inferred previously. Our results provide the first direct evidence, independent of the UV slope, for a correlation between UV and bolometric luminosity (L_(bol)) at high redshift, in the sense that UV-faint galaxies are on average less infrared and less bolometrically luminous than their UV-bright counterparts. The L_(bol)-L_(UV) relation indicates that as the SFR increases, L_(UV) turns over (or "saturates") around the value of L* at z ~ 2, implying that dust obscuration may be largely responsible for modulating the bright end of the UV luminosity function. Finally, dust attenuation is found to correlate with oxygen abundance at z ~ 2. Accounting for systematic differences in local and high-redshift metallicity calibrations, we find that L* galaxies at z ~ 2, while at least an order of magnitude more bolometrically luminous, exhibit ratios of metals to dust that are similar to those of local starbursts. This result is expected if high-redshift galaxies are forming their stars in a less metal-rich environment compared to local galaxies of the same luminosity, thus naturally leading to a redshift evolution in both the bolometric luminosity-metallicity and bolometric luminosity-obscuration relations.

Item Type:Article
Related URLs:
URLURL TypeDescription
Reddy, Naveen A.0000-0001-9687-4973
Erb, Dawn K.0000-0001-9714-2758
Pettini, Max0000-0002-5139-4359
Steidel, Charles C.0000-0002-4834-7260
Shapley, Alice E.0000-0003-3509-4855
Additional Information:© 2010 American Astronomical Society. Received 2009 October 27; accepted for publication 2010 February 3; published 2010 March 10. We thank the staff of the Keck and Palomar Observatories for their help in obtaining the data presented here. Support for N.A.R. was provided by NASA through Hubble Fellowship grant HST-HF-01223.01 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. Additional support has been provided by research funding for the Spitzer Space Telescope Legacy Science Program, provided by NASA through contracts 1224666 and 1287778, issued by the Jet Propulsion Laboratory, California Institute of Technology. C.C.S. has been supported by grants AST 03-07263 and AST 06-06912 from the National Science Foundation and by the David and Lucile Packard Foundation.
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF-01223.01
NSFAST 03-07263
NSFAST 06-06912
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:dust, extinction; galaxies: abundances; galaxies: evolution; galaxies: high-redshift; infrared: galaxies
Issue or Number:2
Classification Code:PACS: 98.54.Ep; 98.62.Ai; 98.62.Qz; 95.30.Wi; 98.62.Py; 98.62.Bj
Record Number:CaltechAUTHORS:20100407-095436265
Persistent URL:
Official Citation:Naveen A. Reddy et al 2010 ApJ 712 1070 doi: 10.1088/0004-637X/712/2/1070
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17883
Deposited By: Jason Perez
Deposited On:07 Apr 2010 20:36
Last Modified:04 Dec 2019 23:18

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