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The galaxies that reionized the Universe

Raičević, Milan; Theuns, Tom; Lacey, Cedric

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Milan Raičević


The Durham GALFORM semi-analytical galaxy formation model has been shown to reproduce the observed rest-frame 1500-Å luminosity function of galaxies well over the whole redshift range z= 5–10. We show that in this model, this galaxy population also emits enough ionizing photons to reionize the Universe by redshift z= 10, assuming a modest escape fraction of 20 per cent. The bulk of the ionizing photons is produced in faint galaxies during starbursts triggered by galaxy mergers. The bursts introduce a dispersion up to ∼5 dex in galaxy-ionizing luminosity at a given halo mass. Almost 90 per cent of the ionizing photons emitted at z= 10 are from galaxies below the current observational detection limit at that redshift. Photoionization suppression of star formation in these galaxies is unlikely to affect this conclusion significantly, because the gas that fuels the starbursts has already cooled out of their host haloes. The galaxies that dominate the ionizing emissivity at z= 10 are faint, with M1500,AB∼−16, have low star formation rates, Graphic−1, and reside in haloes of mass M∼109 h−1 M⊙.


Raičević, M., Theuns, T., & Lacey, C. (2011). The galaxies that reionized the Universe. Monthly Notices of the Royal Astronomical Society, 410(2), 775-787.

Journal Article Type Article
Publication Date Jan 11, 2011
Deposit Date Jan 20, 2012
Publicly Available Date Dec 15, 2014
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 410
Issue 2
Pages 775-787
Keywords Galaxies: evolution, Galaxies: formation, Galaxies: high-redshift, Intergalactic medium, Dark ages, reionization, first stars.
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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2010 The Authors. Journal compilation © 2010 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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