Evidence for low extinction in actively star-forming galaxies at z > 6.5

F. Walter, R. Decarli, C. Carilli, D. Riechers, F. Bertoldi, A. Wei, P. Cox, R. Neri, R. Maiolino, M. Ouchi, E. Egami, K. Nakanishi

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45 Scopus citations


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 (GRB090423 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., Arp220, M82) and less extreme dust-rich nearby spiral galaxies (e.g., M51) 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 GRB090423, 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.

Original languageEnglish (US)
Article number93
JournalAstrophysical Journal
Issue number2
StatePublished - Jun 20 2012


  • cosmology: observations
  • galaxies: evolution
  • galaxies: formation
  • infrared: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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