Hydrogen reionization in the Illustris universe
Author(s)
Bauer, Andreas; Springel, Volker; Vogelsberger, Mark; Genel, Shy; Torrey, Paul; Sijacki, Debora; Nelson, Dylan; Hernquist, Lars; ... Show more Show less
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Hydrodynamical simulations of galaxy formation such as the Illustris simulations have progressed to a state where they approximately reproduce the observed stellar mass function from high to low redshift. This in principle allows self-consistent models of reionization that exploit the accurate representation of the diffuse gas distribution together with the realistic growth of galaxies provided by these simulations, within a representative cosmological volume. In this work, we apply and compare two radiative transfer algorithms implemented in a GPU-accelerated code to the 106.5-Mpc-wide volume of Illustris in post-processing in order to investigate the reionization transition predicted by this model. We find that the first generation of galaxies formed by Illustris is just about able to reionize the universe by redshift z ∼ 7, provided quite optimistic assumptions about the escape fraction and the resolution limitations are made. Our most optimistic model finds an optical depth of τ ≃ 0.065, which is in very good agreement with recent Planck 2015 determinations. Furthermore, we show that moment-based approaches for radiative transfer with the M1 closure give broadly consistent results with our angular-resolved radiative transfer scheme. In our favoured fiducial model, 20 per cent of the hydrogen is reionized by redshift z = 9.20, and this rapidly climbs to 80 per cent by redshift z = 6.92. It then takes until z = 6.24 before 99 per cent of the hydrogen is ionized. On average, reionization proceeds ‘inside-out’ in our models, with a size distribution of reionized bubbles that progressively features regions of ever larger size while the abundance of small bubbles stays fairly constant.
Date issued
2015-09Department
Massachusetts Institute of Technology. Department of Physics; MIT Kavli Institute for Astrophysics and Space ResearchJournal
Monthly Notices of the Royal Astronomical Society
Publisher
Oxford University Press
Citation
Bauer, Andreas; Springel, Volker; Vogelsberger, Mark; Genel, Shy; Torrey, Paul; Sijacki, Debora; Nelson, Dylan and Hernquist, Lars. “Hydrogen Reionization in the Illustris Universe.” Monthly Notices of the Royal Astronomical Society 453, no. 4 (September 9, 2015): 3594–3611.
Version: Author's final manuscript
ISSN
0035-8711
1365-2966