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 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.
