A nearby GRB host galaxy: VLT/X-shooter observations of HG 031203

TL;DR

This study presents a detailed spectroscopic analysis of the host galaxy of a long-duration gamma-ray burst, revealing its physical properties, chemical composition, and star-formation activity, and suggesting that luminous compact galaxies can host LGRBs.

Contribution

It provides the first comprehensive spectroscopic characterization of HG 031203 using VLT/X-shooter data, including chemical abundances, kinematics, and photoionisation modeling, linking LGRBs to luminous compact galaxies.

Findings

Interstellar oxygen abundance of 12+logO/H=8.20±0.03.

Star-formation rate and stellar mass are comparable to luminous compact galaxies.

Photoionisation models successfully reproduce observed emission lines across optical, NIR, and MIR ranges.

Abstract

(abridged) Long-duration gamma-ray bursts (LGRBs) occur in galaxies of generally low metallicity. We aim at a spectroscopic analysis of HG 031203, the host galaxy of a LRGB burst, to obtain its properties. Based on VLT/X-shooter spectroscopic observations in the wavelength range 3200-24000A, we use standard direct methods to evaluate physical conditions and element abundances. The resolving power of the instrument also allowed us to trace the kinematics of the ionised gas. We derive an interstellar oxygen abundance of 12+logO/H=8.20+/-0.03. The observed fluxes of hydrogen lines correspond to the theoretical recombination values after correction for extinction with a single value C(Hbeta)=1.67. We produce the CLOUDY photoionisation HII region model that reproduces observed emission-line fluxes of different ions in the optical range. This model also predicts emission-line fluxes in the near-infrared (NIR) and mid-infrared (MIR) ranges that agree well with the observed ones. This implies that the star-forming region observed in the optical range is the only source of ionisation and there is no additional source of ionisation seen in the NIR and MIR ranges that is hidden in the optical range.We find that the heavy element abundances, Halpha luminosity, stellar mass, star-formation rate and specific star-formation rate of HG 031203 are in the range that is covered by the luminous compact galaxies (LCGs).This implies that the LCGs with extreme star-formation that also comprise green pea galaxies as a subclass may harbour LGRBs.