CONNECTING GRBs AND ULIRGs: A SENSITIVE, UNBIASED SURVEY FOR RADIO EMISSION FROM GAMMA-RAY BURST HOST GALAXIES AT 0 <z <2.5

Luminous infrared galaxies and submillimeter galaxies contribute significantly to stellar mass assembly and provide an important test of the connection between the gamma-ray burst (GRB) rate and that of overall cosmic star formation. We present sensitive 3 GHz radio observations using the Karl G. Jansky Very Large Array of 32 uniformly selected GRB host galaxies spanning a redshift range from 0 <z <2.5, providing the first fully dust- and sample-unbiased measurement of the fraction of GRBs originating from the universe's most bolometrically luminous galaxies. Four galaxies are detected, with inferred radio star formation rates (SFRs) ranging between 50 and 300M(circle dot) yr(-1). Three of the four detections correspond to events consistent with being optically obscured "dark" bursts. Our overall detection fraction implies that between 9% and 23% of GRBs between 0.5 <z <2.5 occur in galaxies with S-3GHz > 10 mu Jy, corresponding to SFR > 50M(circle dot) yr(-1) at z similar to 1 or > 250M(circle dot) yr(-1) at z similar to 2. Similar galaxies contribute approximately 10%-30% of all cosmic star formation, so our results are consistent with a GRB rate that is not strongly biased with respect to the total SFR of a galaxy. However, all four radio-detected hosts have stellar masses significantly lower than IR/submillimeter-selected field galaxies of similar luminosities. We suggest that the GRB rate may be suppressed in metal-rich environments but independently enhanced in intense starbursts, producing a strong efficiency dependence on mass but little net dependence on bulk galaxy SFR.