Ly+ and ultraviolet emission from high-redshift gamma-ray burst hosts: to what extent do gamma-ray bursts trace star formation? |
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| Authors: | P Jakobsson G Björnsson J P U Fynbo G Jóhannesson J Hjorth B Thomsen P Møller D Watson B L Jensen G Östlin J Gorosabel E H Gudmundsson |
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| Institution: | Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark;Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavík, Iceland;Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Århus C, Denmark;European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748, Garching bei München, Germany;Stockholm Observatory, SE-106 91 Stockholm, Sweden;IAA-CSIC, PO Box 03004, E-18080 Granada, Spain;Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA |
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| Abstract: | We report the result of a search for Lyα emission from the host galaxies of the gamma-ray bursts (GRBs) 030226 ( z = 1.986), 021004 ( z = 2.335) and 020124 ( z = 3.198) . We find that the host galaxy of GRB 021004 is an extended (around 8 kpc) strong Lyα emitter with a rest-frame equivalent width (EW) of 68+12?11Å, and a star formation rate of 10.6 ± 2.0 M⊙ yr?1 . We do not detect the hosts of GRB 030226 and GRB 020124, but the upper limits on their Lyα fluxes do not rule out large rest-frame EWs. In the fields of GRB 021004 and GRB 030226 we find seven and five other galaxies, respectively, with excess emission in the narrow-band filter. These galaxies are candidate Lyα-emitting galaxies in the environment of the host galaxies. We have also compiled a list of all z ? 2 GRB hosts, and demonstrate that a scenario where they trace star formation in an unbiased way is compatible with current observational constraints. Fitting the z = 3 luminosity function (LF) under this assumption results in a characteristic luminosity of R *= 24.6 and a faint-end slope of α=?1.55 , consistent with the LF measured for Lyman-break galaxies. |
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| Keywords: | dust extinction galaxies: evolution galaxies: formation galaxies: high-redshift gamma-rays: bursts |
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