The Optically Unbiased GRB Host (TOUGH) Survey. VI. Radio Observations at z <~ 1 and Consistency with Typical Star-forming Galaxies

Michalowski, M. J. et al.
The objective of this paper is to determine the level of obscured star formation activity and dust attenuation in a sample of gamma-ray burst (GRB) hosts, and to test the hypothesis that GRB hosts have properties consistent with those of the general star-forming galaxy populations. We present a radio continuum survey of all z < 1 GRB hosts in The Optically Unbiased GRB Host (TOUGH) sample supplemented with radio data for all (mostly pre-Swift) GRB-SN hosts discovered before 2006 October. We present new radio data for 22 objects and have obtained a detection for three of them (GRB 980425, 021211, 031203; none in the TOUGH sample), increasing the number of radio-detected GRB hosts from two to five. The star formation rate (SFR) for the GRB 021211 host of 825 M yr -1, the highest ever reported for a GRB host, places it in the category of ultraluminous infrared galaxies. We found that at least 63% of GRB hosts have SFR < 100 M yr -1 and at most 8% can have SFR > 500 M yr -1. For the undetected hosts the mean radio flux (
M.J.M. acknowledges the support of the Science and Technology Facilities Council. The Dark Cosmology Centre is funded by the Danish National Research Foundation. A.K. and D.L.K. are partially supported by NSF Award AST-1008353. L.B. acknowledges partial financial support from the Spanish Ministerio de Ciencia e Innovación project AYA2010-21766-C03-01. J.S.D. acknowledges the support of the Royal Society via a Wolfson Research Merit award, and also the support of the European Research Council via the award of an Advanced Grant.