The metallicity of the long GRB hosts and the Fundamental Metallicity Relation of low-mass galaxies

Understand

We investigate the metallicity properties of host galaxies of long Gamma-ray Bursts (GRBs) in the light of the Fundamental Metallicity Relation (FMR), the tight dependence of metallicity on mass and SFR recently discovered for SDSS galaxies with stellar masses above 10^9.2 Msun.

• As most of the GRB hosts have masses below this limit, the FMR can only be used after an extension towards lower masses.
• At this aim, we study the FMR for galaxies with masses down to ~10^8.3 Msun, finding that the FMR does extend smoothly at lower masses, albeit with a much larger scatter.
• We then compare the resulting FMR with the metallicity properties of 18 host galaxies of long GRBs.