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Binary Stars Can Provide the “Missing Photons” Needed for Reionization

Ma, Xiangcheng and Hopkins, Philip F. and Kasen, Daniel and Quataert, Eliot and Faucher-Giguère, Claude-André and Kereš, Dušan and Murray, Norman (2016) Binary Stars Can Provide the “Missing Photons” Needed for Reionization. Monthly Notices of the Royal Astronomical Society, 459 (4). pp. 3614-3619. ISSN 0035-8711. doi:10.1093/mnras/stw941.

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Empirical constraints on reionization require galactic ionizing photon escape fractions f_(esc) ≳ 20 per cent, but recent high-resolution radiation-hydrodynamic calculations have consistently found much lower values ∼1–5 per cent. While these models include strong stellar feedback and additional processes such as runaway stars, they almost exclusively consider stellar evolution models based on single (isolated) stars, despite the fact that most massive stars are in binaries. We re-visit these calculations, combining radiative transfer and high-resolution cosmological simulations with detailed models for stellar feedback from the Feedback in Realistic Environments project. For the first time, we use a stellar evolution model that includes a physically and observationally motivated treatment of binaries (the Binary Population and Spectral Synthesis model). Binary mass transfer and mergers enhance the population of massive stars at late times (≳3 Myr) after star formation, which in turn strongly enhances the late-time ionizing photon production (especially at low metallicities). These photons are produced after feedback from massive stars has carved escape channels in the interstellar medium, and so efficiently leak out of galaxies. As a result, the time-averaged ‘effective’ escape fraction (ratio of escaped ionizing photons to observed 1500 Å photons) increases by factors ∼4–10, sufficient to explain reionization. While important uncertainties remain, we conclude that binary evolution may be critical for understanding the ionization of the Universe.

Item Type:Article
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URLURL TypeDescription Paper
Ma, Xiangcheng0000-0001-8091-2349
Hopkins, Philip F.0000-0003-3729-1684
Quataert, Eliot0000-0001-9185-5044
Faucher-Giguère, Claude-André0000-0002-4900-6628
Kereš, Dušan0000-0002-1666-7067
Additional Information:© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2016 April 19. Received 2016 April 19; in original form 2016 January 27. We thank Chuck Steidel for helpful discussions and the referee for useful comments. We also thank John Beacom and Mike Shull for helpful suggestions after the paper was submitted to arXiv. The simulations used in this paper were run on XSEDE computational resources (allocations TG-AST120025, TG-AST130039, and TG-AST140023). The analysis was performed on the Caltech compute cluster ‘Zwicky’ (NSF MRI award #PHY-0960291). Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1411920 and CAREER grant #1455342. D. Kasen is supported in part by a Department of Energy Office of Nuclear Physics Early Career Award, and by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Divisions of Nuclear Physics, of the US Department of Energy under Contract No. DE-AC02-05CH11231 and by the NSF through grant AST-1109896. D. Kereš was supported by NSF grant AST-1412153 and funds from the University of California, San Diego. CAFG was supported by NSF through grants AST-1412836 and AST-1517491, by NASA through grant NNX15AB22G, and by STScI through grant HST-AR-14293.001-A. EQ was supported by NASA ATP grant 12-APT12-0183, a Simons Investigator award from the Simons Foundation, and the David and Lucile Packard Foundation.
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Department of Energy (DOE)DE-AC02-05CH11231
University of California, San DiegoUNSPECIFIED
Simons FoundationUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:binaries: general – stars: evolution – galaxies: formation – galaxies: high-redshift – cosmology: theory
Issue or Number:4
Record Number:CaltechAUTHORS:20160202-084712784
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Official Citation:Xiangcheng Ma, Philip F. Hopkins, Daniel Kasen, Eliot Quataert, Claude-André Faucher-Giguère, Dušan Kereš, Norman Murray, and Allison Strom Binary stars can provide the ‘missing photons’ needed for reionization MNRAS (July 11, 2016) Vol. 459 3614-3619 doi:10.1093/mnras/stw941 first published online April 21, 2016
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64150
Deposited By: Ruth Sustaita
Deposited On:02 Feb 2016 22:52
Last Modified:10 Nov 2021 23:26

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