Inhomogeneous reionization models in cosmological hydrodynamical simulations

Journal Article · 03 May 2019 · Monthly Notices of the Royal Astronomical Society

DOI: https://doi.org/10.1093/mnras/stz984 · OSTI ID:1510831

Oñorbe, Jose  ^[1]; Davies, F. B.  ^[2]; Lukić, Z. ^[3]; Hennawi, J. F. ^[2]; Sorini, D. ^[4]

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1. Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK, Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
2. Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany, Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
3. Lawrence Berkeley National Laboratory, CA 94720-8139, USA
4. Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany, Fellow of the International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg (IMPRS-HD), D-69117 Heidelberg, Germany

ABSTRACT In this work we present a new hybrid method to simulate the thermal effects of reionization in cosmological hydrodynamical simulations. The method improves upon the standard approach used in simulations of the intergalactic medium (IGM) and galaxy formation without a significant increase in the computational cost, thereby allowing for efficient exploration of the parameter space. The method uses a small set of phenomenological input parameters, and combines a seminumerical reionization model to solve for the topology of reionization with an approximate model of how reionization heats the IGM, using the massively parallel Nyx hydrodynamics code which is specifically designed to solve for the structure of diffuse IGM gas. We have produced several medium-scale, high-resolution simulations (20483, Lbox = 40 Mpc h−1) with various instantaneous and inhomogeneous $${\rm H \,{\small I}}$$ reionization models that use this new methodology. We study the IGM thermal properties of these models and find that large-scale temperature fluctuations extend well beyond the end of reionization. By analysing the 1D flux power spectrum of these models, we find up to $${\sim } 50{{\ \rm per\ cent}}$$ differences in the large-scale properties (low modes, k ≲ 0.01 s km−1) of the post-reionization power spectrum as a result of the thermal fluctuations. We show that these differences could allow one to distinguish between different reionization scenarios with existing Lyα forest measurements. Finally, we explore the differences in the small-scale cut-off of the power spectrum, finding that, for the same heat input, models show very good agreement provided that the reionization redshift of the instantaneous reionization model occurs at the midpoint of the inhomogeneous model.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1510831
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 3 Vol. 486; ISSN 0035-8711
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United Kingdom
• Language: English