Exploring dust extinction at the edge of reionization

Tayyaba Zafar, Darach J. Watson, Nial R. Tanvir, Johan P. U. Fynbo, Rhaana L. C. Starling, Andrew J. Levan

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


The brightness of gamma-ray burst (GRB) afterglows and their occurrence in young, blue galaxies make them excellent probes to study star-forming regions in the distant universe. We here elucidate dust extinction properties in the early universe through the analysis of the afterglows of all known z > 6 GRBs: GRB 090423, 080913, and 050904, at z = 8.2, 6.69, and 6.295, respectively. We gather all available optical and near-infrared photometry, spectroscopy, and X-ray data to construct spectral energy distributions (SEDs) at multiple epochs. We then fit the SEDs at all epochs with a dust-attenuated power law or broken power law. We find no evidence for dust extinction in GRB 050904 and GRB 090423, with possible evidence for a low level of extinction in GRB 080913. We compare the high redshift GRBs to a sample of lower redshift GRB extinctions and find a lack of even moderately extinguished events (AV ~ 0.3) above z gsim 4. In spite of the biased selection and small number statistics, this result hints at a decrease in dust content in star-forming environments at high redshifts.
Original languageEnglish
Pages (from-to)1-6
Number of pages6
JournalThe Astrophysical Journal: an international review of astronomy and astronomical physics
Issue number1
Publication statusPublished - 1 Jul 2011
Externally publishedYes


  • dark ages, reionization, first stars
  • dust, extinction
  • galaxies: high-redshift
  • gamma-ray burst: individual: (GRB 090423, 080913, and 050904(


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