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Winds of change : reionization by starburst galaxies.

Sharma, M. and Theuns, T. and Frenk, C. S. and Bower, R.G. and Crain, R.A. and Schaller, M. and Schaye, J. (2017) 'Winds of change : reionization by starburst galaxies.', Monthly notices of the Royal Astronomical Society., 468 (2). pp. 2176-2188.


We investigate the properties of the galaxies that reionized the Universe and the history of cosmic reionization using the ‘Evolution and Assembly of Galaxies and their Environments’ (eagle) cosmological hydrodynamical simulations. We obtain the evolution of the escape fraction of ionizing photons in galaxies assuming that galactic winds create channels through which 20 per cent of photons escape when the local surface density of star formation is greater than 0.1 M⊙ yr−1 kpc−2. Such threshold behaviour for the generation of winds is observed, and the rare local objects that have such high star formation surface densities exhibit high escape fractions of ∼10 per cent. In our model, the luminosity-weighted mean escape fraction increases with redshift as f¯esc=0.045((1+z)/4)1.1 f¯esc=0.045((1+z)/4)1.1 at z > 3, and the galaxy number weighted mean as 〈fesc〉 = 2.2 × 10−3 ((1 + z)/4)4, and becomes constant ≈0.2 at redshift z > 10. The escape fraction evolves as an increasingly large fraction of stars forms above the critical surface density of star formation at earlier times. This evolution of the escape fraction, combined with that of the star formation rate density from eagle, reproduces the inferred evolution of the filling factor of ionized regions during the reionization epoch (6 < z < 8), the evolution of the post-reionization (0 ≤ z < 6) hydrogen photoionization rate and the optical depth due to Thomson scattering of the cosmic microwave background photons measured by the Planck satellite.

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Publisher statement:This article has been published in Monthly Notices of the Royal Astronomical Society ©: 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:06 March 2017
Date deposited:17 May 2017
Date of first online publication:09 March 2017
Date first made open access:17 May 2017

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