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Published January 20, 2016 | Published + Submitted
Journal Article Open

The Swift Gamma-Ray Burst Host Galaxy Legacy Survey. I. Sample Selection and Redshift Distribution

Abstract

We introduce the Swift Gamma-Ray Burst Host Galaxy Legacy Survey ("SHOALS"), a multi-observatory high-redshift galaxy survey targeting the largest unbiased sample of long-duration gamma-ray burst (GRB) hosts yet assembled (119 in total). We describe the motivations of the survey and the development of our selection criteria, including an assessment of the impact of various observability metrics on the success rate of afterglow-based redshift measurement. We briefly outline our host galaxy observational program, consisting of deep Spitzer/IRAC imaging of every field supplemented by similarly deep, multicolor optical/near-IR photometry, plus spectroscopy of events without preexisting redshifts. Our optimized selection cuts combined with host galaxy follow-up have so far enabled redshift measurements for 110 targets (92%) and placed upper limits on all but one of the remainder. About 20% of GRBs in the sample are heavily dust obscured, and at most 2% originate from z > 5.5. Using this sample, we estimate the redshift-dependent GRB rate density, showing it to peak at z ~ 2.5 and fall by at least an order of magnitude toward low (z = 0) redshift, while declining more gradually toward high (z ~ 7) redshift. This behavior is consistent with a progenitor whose formation efficiency varies modestly over cosmic history. Our survey will permit the most detailed examination to date of the connection between the GRB host population and general star-forming galaxies, directly measure evolution in the host population over cosmic time and discern its causes, and provide new constraints on the fraction of cosmic star formation occurring in undetectable galaxies at all redshifts.

Additional Information

© 2016 The American Astronomical Society. Received 2015 April 9; accepted 2015 October 31; published 2016 January 19. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. It is also based in part on observations with the NASA/ESA Hubble Space Telescope, obtained from the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-90062. Support for this work was provided by NASA through an award issued by JPL/Caltech and through Hubble Fellowship grant HST-HF-51296.01-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. D.A.P. further acknowledges support from a Marie Sklodowska-Curie Individual Fellowship within the Horizon 2020 European Union (EU) Framework Programme for Research and Innovation (H2020-MSCA-IF-2014-660113). The Dark Cosmology Centre is funded by the DNRF. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Program (FP7/2007–2013)/ERC Grant agreement no. EGGS-278202. S.S. acknowledges support from CONICYT-Chile FONDECYT 3140534, Basal-CATA PFB-06/2007, and Project IC120009 "Millennium Institute of Astrophysics (MAS) of Iniciativa Científica Milenio del Ministerio de Economía, Fomento y Turismo. S.K. acknowledges support from FONDECYT 3130488. A.C. is supported by the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Oak Ridge Associated Universities through a contract with NASA. A.d.U.P. and C.C.T. are supported by Ramón y Cajal fellowships. Some of the data presented here were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory and on observations made with the Gran Telescopio Canarias (GTC). Part of the funding for GROND (both hardware and personnel) was generously granted from the Leibniz-Prize to Prof. G. Hasinger (DFG grant HA 1850/28-1). It is a pleasure to thank the Swift team for creating such a superbly prolific and successful instrument, without which this study would have been impossible. We also wish to extend thanks to the entire ground-based GRB follow-up community for providing many of the afterglow identifications and redshifts critical to our study. We particularly acknowledge D. Malesani, Y. Urata, and K. Huang for providing improved afterglow positions and images, and we thank the anonymous referee and D. A. Kann for useful comments. We also thank our other collaborators for assistance with acquiring ground-based observations, including R. Sanchez Ramirez, F. E. Bauer, and P. Schady. We thank B. Robertson and M. Trenti for useful discussions and also thank B. Robertson for providing the most up-to-date SFR density curves. Facilities: Spitzer:IRAC - Spitzer Space Telescope satellite, Keck-I:LRIS - , Keck-I:MOSFIRE - , HST:WFC3 - Hubble Space Telescope satellite, VLT:X-shooter - , GTC:OSIRIS - Gran Telescopio CANARIAS 10.4m telescope (GRANTECAN), Max Planck:2.2 m (GROND) - , PO:1.5 m - .

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Published - Perley_2016p7.pdf

Submitted - 1504.02482v4.pdf

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August 20, 2023
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