Journal
ASTROPHYSICAL JOURNAL
Volume 735, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/735/1/2
Keywords
dark ages, reionization, first stars; dust, extinction; galaxies: high-redshift; gamma-ray burst: individual: (GRB 090423, 080913 and 050904)
Categories
Funding
- Danish National Research Foundation
- STFC [ST/I001719/1, ST/H001972/1, PP/E002064/1, ST/F002599/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/H001972/1, PP/E002064/1, ST/F002599/1, ST/I001719/1] Funding Source: researchfish
- Direct For Mathematical & Physical Scien [0847563] Funding Source: National Science Foundation
- Division Of Astronomical Sciences [0847563] Funding Source: National Science Foundation
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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 (A(V) similar to 0.3) above z greater than or similar to 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.
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