Luminosity Distribution of Gamma-Ray Burst Host Galaxies at Redshift = 1 in Cosmological Simulation

Abstract

Long Gamma‐Ray Bursts (GRBs) are the brightest astronomical transient events which provide us clues to study high redshift universe. It is broadly accepted that at least some of the long GRBs originate from dying massive stars. Therefore GRBs can be used as a tracer of star formation which is detectable to very high redshift (z≳10). However, studies using stellar evolution models suggest that GRBs do not simply trace star formation, but preferentially occur in low‐metallicity environment. The observational evidence is still controversial. We need to understand the low‐metallicity preference of long GRBs before using them as a probe to the high redshift universe. To study the low‐metallicity preference, we construct first numerical model of GRB host galaxies that can quantitatively reproduce luminosity distribution of GRB host galaxies. Using cosmological smoothed particle hydrodynamic simulations, we compute the UV luminosity distribution of GRB host galaxies for two different cases: (i) GRBs simply trace star formation, and (ii) GRBs preferentially occur in low‐metallicity environment. We compare the simulation with observations, and discuss the low‐metallicity preference of GRBs. Our model reproduce the observed luminosity probability distribution function of GRB host galaxies when we assume that GRBs originate from stars with metallicities Z≲0.1 Z⊙, supporting the suggestion from the theoretical studies.