Abstract
Whether stars could have driven the reionization of the intergalactic medium depends critically on the proportion of ionizing radiation that escapes the galaxies in which it is produced. Spectroscopy of gamma-ray burst (GRB) afterglows can be used to estimate the opacity to extreme ultraviolet (EUV) radiation along the lines-of-sight to the bursts. Assuming that long-duration GRBs trace the locations of the massive stars dominating EUV production, the average escape fraction of ionizing radiation can be calculated independently of galaxy size or luminosity. Here we present a compilation of H i column density (N HI ) measures for 140 GRBs in the range 1.6 < z < 6.7. Although the sample is heterogeneous, in terms of spectral resolution and signal-to-noise ratio, fits to the Ly α absorption line provide robust constraints on N HI , even for spectra of insufficient quality for other purposes. Thus we establish an escape fraction at the Lyman limit of (f esc ) ≈ 0.005, with a 98 per cent confidence upper limit of (f esc ) ≈ 0.015. This analysis suggests that stars provide a small contribution to the ionizing radiation budget at z < 5. At higher redshifts firm conclusions are limited by the small size of the GRB sample (7/140), but any decline in average H i column density seems to be modest. We also find no significant correlation of N HI with galaxy UV luminosity or host stellar mass. We discuss in some detail potential biases and argue that, while not negligible, systematic errors in f esc are unlikely to be more than a factor ~2 in either direction, and so would not affect the primary conclusions. Given that many GRB hosts are low-metallicity dwarf galaxies with high specific star-formation rates, these results present a particular problem for the hypothesis that such galaxies dominated the reionization of the Universe.
| Original language | English |
|---|---|
| Pages (from-to) | 5380-5408 |
| Number of pages | 29 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 483 |
| Issue number | 4 |
| Early online date | 20 Dec 2018 |
| DOIs | |
| Publication status | Published - 11 Mar 2019 |
Funding
Partly based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovac¸ão (Brazil). Partially based on data from the Grand Telescopio Canarias (GTC) Public Archive at the Centro de Astrobiología (CAB), under the Spanish Research Council (CSIC) and the National Institute of Technical Aerospace (INTA). JJ acknowledges support from Nederlandse Onderzoekschool Voor Astronomie(NOVA) and The Netherlands Organisation for Scientific Research (NWO) - The São Paulo Research Foundation (FAPESP) grant for advanced instrumentation in astronomy. KEH acknowledges support by a Project Grant (162948–051) from The Icelandic Research Fund. AJL and ERS acknowledge Science and Technology Facilities Council (STFC) consolidated grant ST/L000733/1. NRT and KW acknowledge Science and Technology Facilities Council (STFC) consolidated grant ST/N000757/1. AC acknowledges National Aeronautics and Space Administration (NASA) grant NNX15AP95A. AdUP acknowledges support from a Ramón y Cajal fellowship (RyC-2012-09975), a 2016 Banco Bilbao Vizcaya Argentaria (BBVA) Foundation Grant for Researchers and Cultural Creators, and from the Spanish research project AYA 2014-58381-P. RC acknowledges partial support from National Aeronautics and Space Administration (NASA) Swift grant NNX16AB04G. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation Grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The Sloan Digital Sky Survey-III (SDSS-III) web site is http://www.sdss3.org/. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 725246). 1Department of Physics & Astronomy and Leicester Institute of Space & Earth Observation, University of Leicester, University Road, Leicester LE1 7RH, UK 2Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark 3Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la As-tronomía s/n, E-18008 Granada, Spain 4Astronomical Institute Anton Pannekoek, University of Amsterdam, PO Box 94249, NL-1090 GE Amsterdam, the Netherlands 5Department of Physics, University of Warwick, Coventry CV4 7AL, UK 6Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK 7NASA’s Goddard Space Flight Center, Greenbelt, MD 20771, USA 8Joint Space-Science Institute, University of Maryland, College Park, MD 20742, USA 9Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 10Astrophysical Institute, Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA 11INAF-Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Mer-ate, Italy 12College of Science and Mathematics, University of the Virgin Islands, #2 Brewers Bay Road, Charlotte Amalie, USVI 00802 13INAF - Osservatorio Astronomico di Roma, Via Frascati 33, 00040, I-00078, Monte Porzio Catone (RM), Italy 14ASI-Science Data Centre, Via del Politecnico, snc, I-00133 Rome, Italy 15INAF-IASF Milano, Via E. Bassini 15, I-20133 Milano, Italy 16APC, Astroparticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, 10, Rue Alice Domon et Léonie Duquet, F-75205 Paris Cedex 13, France 17Centre for Astrophysics and Cosmology, University of Nova Gorica, Vipavska 11c, 5270 Ajdovsˇcˇina, Slovenia 18Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavík, Iceland 19Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching, Germany 20Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY, UK 21Department of Astronomy, University of California, 501 Campbell Hall, Berkeley, CA 94720-3411, USA 22Istituto di Astrofisica Spaziale E Fisica Cosmica di Bologna Area della Ricerca, via Piero Gobetti, 101, I-40129 Bologna, Italy 23Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 7610001, Israel 24Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg, Germany 25GEPI, Observatoire de Paris, PSL Research University, CNRS, Univ. Paris Diderot, Sorbonne Paris Cité, Place Jules Janssen, F-92195 Meudon, France 26Department of Astrophysics, Radboud University Nijmegen, P.O. Box 9010, NL-6500 GL Nijmegen, The Netherlands 27CAS Key Laboratory of Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
Keywords
- dark ages, reionization, first stars
- galaxies: ISM
- gamma-ray burst: general
- intergalactic medium
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science