GRB hosts through cosmic time

Abstract

[Abridged] We present data and initial results from VLT/X-Shooter emission-line spectroscopy of 96 GRB-selected galaxies at 0.1 <1 in the adopted metallicity scale. This is significantly less than the fraction of star formation in similar galaxies, illustrating that GRBs are scarce in high-metallicity environments. At z~3, sensitivity limits us to probing only the most luminous GRB hosts for which we derive metallicities of Z ~< 0.5 Z_sun. Together with a high incidence of galaxies with similar metallicity in our sample at z~1.5, this indicates that the metallicity dependence observed at low redshift will not be dominant at z~3.