THE HOST GALAXIES OF SWIFT DARK GAMMA-RAY BURSTS: OBSERVATIONAL CONSTRAINTS ON HIGHLY OBSCURED AND VERY HIGH REDSHIFT GRBs

Journal Article · Tue Dec 15 00:00:00 EST 2009 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/138/6/1690; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21301510

Perley, D A; Cenko, S B; Bloom, J S; Butler, N R; Starr, D ^[1]; Chen, H -W ^[2]; Kocevski, D ^[3]; Prochaska, J X ^[4]; Brodwin, M; Soderberg, A M ^[5]; Glazebrook, K ^[6]; Kasliwal, M M; Kulkarni, S R; Ofek, E O ^[7]; Lopez, S ^[8]

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1. Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
2. Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave, Chicago, IL 60637 (United States)
3. Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 2575 Sand Hill Road M/S 29, Menlo Park, CA 94025 (United States)
4. Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
5. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
6. Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122 (Australia)
7. Department of Astronomy, California Institute of Technology, M/C 249-17, Pasadena, CA 91125 (United States)
8. Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile)

In this work, we present the first results of our imaging campaign at Keck Observatory to identify the host galaxies of 'dark' gamma-ray bursts (GRBs), events with no detected optical afterglow or with detected optical flux significantly fainter than expected from the observed X-ray afterglow. We find that out of a uniform sample of 29 Swift bursts rapidly observed by the Palomar 60 inch telescope through 2008 March (14 of which we classify as dark), all events have either a detected optical afterglow, a probable optical host-galaxy detection, or both. Our results constrain the fraction of Swift GRBs coming from very high redshift (z>7), such as the recent GRB 090423, to between 0.2% and 7% at 80% confidence. In contrast, a significant fraction of the sample requires large extinction columns (host-frame A{sub V} {approx}> 1 mag, with several events showing A{sub V} > 2-6 mag), identifying dust extinction as the dominant cause of the dark GRB phenomenon. We infer that a significant fraction of GRBs (and, by association, of high-mass star formation) occurs in highly obscured regions. However, the host galaxies of dark GRBs seem to have normal optical colors, suggesting that the source of obscuring dust is local to the vicinity of the GRB progenitor or highly unevenly distributed within the host galaxy.

• OSTI ID: 21301510
• Journal Information: Astronomical Journal (New York, N.Y. Online), Vol. 138, Issue 6; Other Information: DOI: 10.1088/0004-6256/138/6/1690; Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
AFTERGLOW
COSMIC GAMMA BURSTS
DUSTS
GALAXIES
PHOTOMETRY
RED SHIFT
STARS
TELESCOPES