The Swift GRB Host Galaxy Legacy Survey. II. Rest-frame Near-IR Luminosity Distribution and Evidence for a Near-solar Metallicity Threshold

Citation:

Perley DA, Tanvir NR, Hjorth J, Laskar T, Berger E, Chary R, de Ugarte Postigo A, Fynbo JPU, Krühler T, Levan AJ, et al. The Swift GRB Host Galaxy Legacy Survey. II. Rest-frame Near-IR Luminosity Distribution and Evidence for a Near-solar Metallicity Threshold. The Astrophysical Journal [Internet]. 2016;817.

Date Published:

January 1, 2016

Abstract:

We present rest-frame near-IR (NIR) luminosities and stellar masses fora large and uniformly selected population of gamma-ray burst (GRB) hostgalaxies using deep Spitzer Space Telescope imaging of 119 targets fromthe Swift GRB Host Galaxy Legacy Survey spanning 0.03 < z < 6.3,and we determine the effects of galaxy evolution and chemical enrichmenton the mass distribution of the GRB host population across cosmichistory. We find a rapid increase in the characteristic NIR hostluminosity between z ˜ 0.5 and z ˜ 1.5, but little variationbetween z ˜ 1.5 and z ˜ 5. Dust-obscured GRBs dominate themassive host population but are only rarely seen associated withlow-mass hosts, indicating that massive star-forming galaxies areuniversally and (to some extent) homogeneously dusty at high redshiftwhile low-mass star-forming galaxies retain little dust in theirinterstellar medium. Comparing our luminosity distributions with fieldsurveys and measurements of the high-z mass-metallicity relation,our results have good consistency with a model in which the GRB rate perunit star formation is constant in galaxies with gas-phase metallicitybelow approximately the solar value but heavily suppressed in moremetal-rich environments. This model also naturally explains thepreviously reported “excess” in the GRB rate beyond z ≳2 metals stifle GRB production in most galaxies at z < 1.5 but haveonly minor impact at higher redshifts. The metallicity threshold weinfer is much higher than predicted by single-star models and favors abinary progenitor. Our observations also constrain the fraction ofcosmic star formation in low-mass galaxies undetectable to Spitzer to besmall at z < 4.

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