Revisiting Metallicity of Long Duration Gamma-Ray Burst Host Galaxies: The Role of Chemical Inhomogeneity within Galaxies

Understand

We predict the metallicity probability distribution function (PDF) of long gamma-ray burst (GRB) host galaxies at low-redshifts ($z \la 0.3$) when GRBs occur only in low-metallicity environment, assuming empirical formulations of galaxy properties.

• We discuss contribution of high-metallicity galaxies to the cosmic rate of low-metallicity GRBs, taking internal dispersion of metallicity within each galaxy into account.
• Assuming GRBs trace low-metallicity star formation $< \Zcrit$: 12+log$_{10}$(O/H) = 8.2, we find that GRB host galaxies may have systematically higher-metallicity than that of GRB progenitors.
• Furthermore, we expect $\ga$ 10% of the host galaxies to have 12+log$_{10}$(O/H) $> 8.8$, if galaxies have internal dispersion of metallicity comparable to that observed in the Milky Way.