The chemical enrichment of long-GRB nurseries up to z=2

Understand

We investigate the existence of a metallicity threshold for the production of long gamma-ray bursts (LGRBs).

• We used the host galaxies of the Swift/BAT6 sample of LGRBs.
• We considered the stellar mass, star formation rate (SFR), and metallicity determined from the host galaxy photometry and spectroscopy up to z = 2 and used them to compare the distribution of host galaxies to that of field galaxies in the mass-metallicity and fundamental metallicity relation plane.
• We find that although LGRBs also form in galaxies with relatively large stellar masses, the large majority of host galaxies have metallicities below log(O=H)~8.6.