Connecting GRBs and ULIRGs: A Sensitive, Unbiased Survey for Radio Emission from Gamma-Ray Burst Host Galaxies at 0<z<2.5

TL;DR

This study uses sensitive radio observations to investigate the connection between gamma-ray burst host galaxies and luminous infrared galaxies, revealing that GRBs are not strongly biased towards star-formation rate but may depend on galaxy mass and environment.

Contribution

First fully dust- and sample-unbiased radio survey of GRB hosts across 0<z<2.5, providing new insights into GRB host galaxy properties and their relation to star formation.

Findings

9-23% of GRBs occur in high SFR galaxies at 0.5<z<2.5

Radio-detected hosts have modest stellar masses (~10^10 Msun)

Results suggest GRB rate depends on galaxy mass and environment, not just star-formation rate.

Abstract

Luminous infrared galaxies and submillimeter galaxies contribute significantly to stellar mass assembly and the frequency of GRBs in these systems provides an important test of the connection between the gamma-ray burst 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 ranging between 50-300 Msun/yr. Three of the four detections correspond to events consistent with being optically-obscured "dark" bursts. Our overall detection fraction implies that between 9-23% of GRBs between 0.5 < z < 2.5 occur in galaxies with S_3GHz > 10 uJy, corresponding to SFR >50 Msun/yr at z~1 or >250 Msun/yr at z~2. Similar galaxies contribute approximately 10-30% of all cosmic star-formation, so our results are consistent with a GRB rate which is not strongly biased with respect to the total star-formation rate of a galaxy. However, all four radio-detected hosts have modest stellar masses (~few x 10^10 Msun), 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 star-formation rate.