Investigating a population of infrared-bright gamma-ray burst host galaxies

TL;DR

This study identifies and characterizes infrared-bright gamma-ray burst host galaxies using multi-wavelength data, revealing biases towards low redshift, high stellar mass, and high attenuation, and providing insights into the diversity of GRB host environments.

Contribution

The paper introduces a new methodology combining WISE data with follow-up observations to identify IR-bright GRB hosts and compares their properties to existing host galaxy populations.

Findings

IR-bright GRB hosts are biased towards low redshift and dusty environments.

The methodology successfully identified new candidate hosts, including previously unknown ones.

IR-bright hosts are not a distinct class but help constrain the broader GRB host population.

Abstract

We identify and explore the properties of an infrared-bright gamma-ray burst (GRB) host population. Candidate hosts are selected by coincidence with sources in WISE, with matching to random coordinates and a false alarm probability analysis showing that the contamination fraction is approx 0.5. This methodology has already identified the host galaxy of GRB 080517. We combine survey photometry from Pan-STARRS, SDSS, APASS, 2MASS, GALEX and WISE with our own WHT/ACAM and VLT/X- shooter observations to classify the candidates and identify interlopers. Galaxy SED fitting is performed using MAGPHYS, in addition to stellar template fitting, yielding 13 possible IR-bright hosts. A further 7 candidates are identified from previously published work. We report a candidate host for GRB 061002, previously unidentified as such. The remainder of the galaxies have already been noted as potential hosts. Comparing the IR-bright population properties including redshift z, stellar mass M*, star formation rate SFR and V-band attenuation Av to GRB host catalogues in the literature, we find that the infrared-bright population is biased toward low z, high M* and high Av. This naturally arises from their initial selection - local and dusty galaxies are more likely to have the required IR flux to be detected in WISE. We conclude that while IR-bright GRB hosts are not a physically distinct class, they are useful for constraining existing GRB host populations, particularly for long GRBs.