Simulating high-z Gamma-ray Burst host galaxies

TL;DR

This study uses advanced simulations to characterize the properties of high-redshift gamma-ray burst host galaxies, revealing they are faint, low-mass, and metal-poor, and likely play a key role in cosmic re-ionization.

Contribution

It provides a detailed physical description of high-z LGRB host galaxies using simulations, linking their properties to galaxy formation and re-ionization.

Findings

LGRB hosts at z>6 have low SFR, stellar mass, and metallicity.

Their UV luminosity is below current detection limits.

They trace faint galaxies critical for re-ionization.

Abstract

We investigate the nature of high-z host galaxies of long Gamma-Ray Bursts (LGRBs) by means of state-of-the-art numerical simulations of cosmic structure formation and evolution of galaxies. We combine results from different runs with various box sizes and resolutions. By assigning to each simulated galaxy the probability to host a LGRB, assumed to be proportional to the mass of young stars, we provide a full description of the physical properties of high-z LGRB host galaxy population. We find that LGRBs at z>6 are hosted in galaxies with typical star formation rates SFR \sim 0.03-0.3 Msun yr^{-1}, stellar masses M \sim 10^{6-8} Msun, and metallicities Z \sim 0.01-0.1 Zsun. Furthermore, the ratio between their doubling time and the corresponding cosmic time seems to be universally equal to ~0.1-0.3, independently from the redshift. The distribution of their UV luminosity places LGRB hosts in the faint-end of the galaxy luminosity function, well below the current capabilities of space- or ground-based optical facilities. This is in line with recent reports of non-detection of LGRB hosts using extremely deep HST and VLT observations. In conclusion, high-z LGRBs are found to trace the position of those faint galaxies that are thought to be the major actors in the re-ionization of the Universe.