Radio Observations of GRB Host Galaxies

TL;DR

This study uses radio observations at 5.5 and 9.0 GHz to analyze star formation in 17 GRB host galaxies at redshifts 0.5 to 1.4, finding limited radio detections and exploring their implications for star formation activity.

Contribution

It provides new radio continuum measurements of GRB host galaxies and investigates their star formation properties, including the nature of detected emissions and comparison with supernova hosts.

Findings

Four sources detected, one likely due to afterglow emission.

No strong evidence for redshift evolution in GRB host star formation rates.

Higher detection rate of 'dark' bursts than expected.

Abstract

We present 5.5 and 9.0 GHz observations of a sample of seventeen GRB host galaxies at 0.5<z<1.4, using the radio continuum to explore their star formation properties in the context of the small but growing sample of galaxies with similar observations. Four sources are detected, one of those (GRB 100418A) likely due to lingering afterglow emission. We suggest that the previously-reported radio afterglow of GRB 100621A may instead be due to host galaxy flux. We see no strong evidence for redshift evolution in the typical star formation rate of GRB hosts, but note that the fraction of `dark' bursts with detections is higher than would be expected given constraints on the more typical long GRB population. We also determine the average radio-derived star formation rates of core collapse supernovae at comparable redshift, and show that these are still well below the limits obtained for GRB hosts, and show evidence for a rise in typical star formation rate with redshift in supernova hosts.