Reionization with Simba: How much does astrophysics matter in modeling cosmic reionization?

Abstract

Traditional large-scale models of reionization usually employ simple deterministic relations between halo mass and luminosity to predict how reionization proceeds. We here examine the impact on modelling reionization of using more detailed models for the ionizing sources as identified within the $100Mpc/h$ cosmological hydrodynamic simulation {\sc Simba}, coupled with post-processed radiative transfer. Comparing with simple (one-to-one) models, the main difference of using {\sc Simba} sources is the scatter in the relation between dark matter halos and star formation, and hence ionizing emissivity. We find that, at the power spectrum level, the ionization morphology remains mostly unchanged, regardless of the variability in the number of sources or escape fraction. In particular, the power spectrum shape remains unaffected and its amplitude changes slightly by less than 5-10\%, throughout reionization, depending on the scale and neutral fraction. Our results show that simplified models of ionizing sources remain viable to efficiently model the structure of reionization on cosmological scales, although the precise progress of reionization requires accounting for the scatter induced by astrophysical effects.

13 pages, 6 figures, accepted to ApJ

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• HIFlow: Generating Diverse HI Maps and Inferring Cosmology while Marginalizing over Astrophysics using Normalizing Flows
• The importance of stochasticity in determining galaxy emissivities and UV LFs during cosmic dawn and reionization
• Late-end reionization with ATON-HE: towards constraints from Lyman-$\alpha$ emitters observed with JWST
• Efficient simulation of discrete galaxy populations and associated radiation fields during the first billion years
• Explaining JWST star formation history at $z\sim 17$ by modifying $\Lambda$CDM
• Impact of astrophysical scatter on the Epoch of Reionization [H I]${}_{21cm}$ bispectrum