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A population of massive, luminous galaxies hosting heavily dust-obscured gamma-ray bursts: Implications for the use of grbs as tracers of cosmic star formation

Perley, DA and Levan, AJ and Tanvir, NR and Cenko, SB and Bloom, JS and Hjorth, J and Krühler, T and Filippenko, AV and Fruchter, A and Fynbo, JPU and Jakobsson, P and Kalirai, J and Milvang-Jensen, B and Morgan, AN and Prochaska, JX and Silverman, JM (2013) A population of massive, luminous galaxies hosting heavily dust-obscured gamma-ray bursts: Implications for the use of grbs as tracers of cosmic star formation. The Astrophysical Journal, 778 (2). ISSN 1538-4357

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We present observations and analysis of the host galaxies of 23 heavily dust-obscured gamma-ray bursts (GRBs) observed by the Swift satellite during the years 2005-2009, representing all GRBs with an unambiguous host-frame extinction of AV > 1 mag from this period. Deep observations with Keck, Gemini, Very Large Telescope, Hubble Space Telescope, and Spitzer successfully detect the host galaxies and establish spectroscopic or photometric redshifts for all 23 events, enabling us to provide measurements of the intrinsic host star formation rates, stellar masses, and mean extinctions. Compared to the hosts of unobscured GRBs at similar redshifts, we find that the hosts of dust-obscured GRBs are (on average) more massive by about an order of magnitude and also more rapidly star forming and dust obscured. While this demonstrates that GRBs populate all types of star-forming galaxies, including the most massive, luminous systems at z ≈ 2, at redshifts below 1.5 the overall GRB population continues to show a highly significant aversion to massive galaxies and a preference for low-mass systems relative to what would be expected given a purely star-formation-rate-selected galaxy sample. This supports the notion that the GRB rate is strongly dependent on metallicity, and may suggest that the most massive galaxies in the universe underwent a transition in their chemical properties ∼9 Gyr ago. We also conclude that, based on the absence of unobscured GRBs in massive galaxies and the absence of obscured GRBs in low-mass galaxies, the dust distributions of the lowest-mass and the highest-mass galaxies are relatively homogeneous, while intermediate-mass galaxies (∼109 M ⊙) have diverse internal properties. © 2013. The American Astronomical Society. All rights reserved.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences, 0305 Organic Chemistry, 0306 Physical Chemistry (Incl. Structural)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society
Date Deposited: 18 May 2017 08:20
Last Modified: 18 May 2017 08:20
DOI or Identification number: 10.1088/0004-637X/778/2/128
URI: http://researchonline.ljmu.ac.uk/id/eprint/6457

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