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Evidence for Low Extinction in Actively Star-forming Galaxies at z > 6.5

Walter, F. and Decarli, R. and Carilli, C. L. and Riechers, D. and Bertoldi, F. and Weiss, A. and Cox, P. and Maiolino, R. and Ouchi, M. and Egami, E. and Nakanishi, K. and Neri, R. (2012) Evidence for Low Extinction in Actively Star-forming Galaxies at z > 6.5. Astrophysical Journal, 752 (2). Art. No. 93. ISSN 0004-637X. doi:10.1088/0004-637X/752/2/93.

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We present a search for the [C II] 158 μm fine structure line (a main cooling line of the interstellar medium) and the underlying far-infrared (FIR) continuum in three high-redshift (6.6 < z < 8.2) star-forming galaxies using the IRAM Plateau de Bure Interferometer. We targeted two Lyα-selected galaxies (Lyα emitters, LAEs) with moderate UV-based star formation rates (SFRs ~ 20 M_☉ yr^(–1); Himiko at z = 6.6 and IOK-1 at z = 7.0) and a gamma-ray burst (GRB) host galaxy (GRB 090423 at z ~ 8.2). Based on our 3σ rest-frame FIR continuum limits, previous (rest-frame) UV continuum measurements and spectral energy distribution (SED) fitting, we rule out SED shapes similar to highly obscured galaxies (e.g., Arp 220, M 82) and less extreme dust-rich nearby spiral galaxies (e.g., M 51) for the LAEs. Conservatively assuming an SED shape typical of local spiral galaxies we derive upper limits for the FIR-based star formation rates (SFRs) of ~70 M_☉ yr^(–1), ~50 M_☉ yr^(–1), and ~40 M_☉ yr^(–1) for Himiko, IOK-1, and GRB 090423, respectively. For the LAEs these limits are only a factor ~3 higher than the published UV-based SFRs (uncorrected for extinction). This indicates that the dust obscuration in the z > 6 LAEs studied here is lower by a factor of a few than what has recently been found in some LAEs at lower redshift (2 < z < 3.5) with similar UV-based SFRs. A low obscuration in our z > 6 LAE sample is consistent with recent rest-frame UV studies of z ~ 7 Lyman break galaxies.

Item Type:Article
Related URLs:
URLURL TypeDescription
Walter, F.0000-0003-4793-7880
Decarli, R.0000-0002-2662-8803
Carilli, C. L.0000-0001-6647-3861
Riechers, D.0000-0001-9585-1462
Bertoldi, F.0000-0002-1707-1775
Weiss, A.0000-0003-4678-3939
Cox, P.0000-0003-2027-8221
Ouchi, M.0000-0002-1049-6658
Nakanishi, K.0000-0002-6939-0372
Neri, R.0000-0002-7176-4046
Additional Information:© 2012 The American Astronomical Society. Received 2011 November 18; accepted 2012 April 13; published 2012 May 30. We thank the referee for critical and constructive comments that helped to improve this paper. We thank Dale Frail and Ruben Salvaterra for useful discussions concerning GRB host galaxies. Based on observations with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). R.D. is supported by DLR grant FKZ-50-OR-1104. D.R. acknowledges funding through a Spitzer Space Telescope grant. We acknowledge the use of GILDAS software (
Funding AgencyGrant Number
Institut national des sciences de l'Univers (INSU)UNSPECIFIED
Instituto Geográfico Nacional (IGN)UNSPECIFIED
Deutschen Zentrums für Luft- und Raumfahrt (DLR)FKZ-50-OR-1104
Spitzer Space TelescopeUNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Subject Keywords:cosmology: observations; galaxies: evolution; galaxies: formation; infrared: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20120724-094027948
Persistent URL:
Official Citation:Evidence for Low Extinction in Actively Star-forming Galaxies at z > 6.5 F. Walter et al. 2012 ApJ 752 93
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:32664
Deposited By: Ruth Sustaita
Deposited On:24 Jul 2012 16:57
Last Modified:09 Nov 2021 21:29

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