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

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 <italic>WISE</italic>, with matching to random coordinates and a false alarm probability analysis showing that the contamination fraction is ∼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 <italic>WISE</italic> 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 seven candidates are identified from the 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 <italic>z</italic>, stellar mass <italic>M</italic>⋆, star formation rate SFR, and <italic>V</italic>-band attenuation <italic>A</italic>V to GRB host catalogues in the literature, we find that the infrared-bright population is biased towards low <italic>z</italic>, high <italic>M</italic>⋆, and high <italic>A</italic>V. This naturally arises from their initial selection – local and dusty galaxies are more likely to have the required IR flux to be detected in <italic>WISE</italic>. 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. [ABSTRACT FROM AUTHOR]