The Host Galaxies of Gamma-Ray Bursts I: ISM Properties of Ten Nearby Long-Duration GRB Hosts

TL;DR

This study investigates the interstellar medium properties of nearby long-duration gamma-ray burst host galaxies, revealing they typically have low metallicity environments distinct from other galaxy populations, which impacts their use as star formation tracers.

Contribution

First large-scale survey providing detailed ISM diagnostics of nearby LGRB hosts, comparing their properties to various galaxy populations and models.

Findings

LGRB hosts generally have low-metallicity ISM environments.

Their ISM properties differ significantly from other galaxy types.

LGRB hosts are not representative of the general galaxy population.

Abstract

We present the first observations from a large-scale survey of nearby (z < 1) long-duration gamma-ray burst (LGRB) host galaxies, which consist of eight rest-frame optical spectra obtained at Keck and Magellan. Along with two host galaxy observations from the literature, we use optical emission line diagnostics to determine metallicities, ionization parameters, young stellar population ages, and star formation rates. We compare the LGRB host environments to a variety of local and intermediate-redshift galaxy populations, as well as the newest grid of stellar population synthesis and photoionization models generated with the Starburst99/Mappings codes. With these comparisons we investigate whether the GRB host galaxies are consistent with the properties of the general galaxy population, and therefore whether they may be used as reliable tracers of star formation. We find that LGRB host galaxies generally have low-metallicity ISM environments out to z ~ 1. The ISM properties of our GRB hosts, including metallicity, ionization parameter, and young stellar population age, are significantly different from the general galaxy population, host galaxies of nearby broad-lined Type Ic supernovae, and nearby metal-poor galaxies.