This paper (link) improves on existing reionisation simulations in two ways: by including helium in the radiative transfer simulations that are done in post-processing and by modeling the ionising emissivities in such a way that they are consistent with the observational constraints on the Thomson scattering optical depth and hydrogen photo-ionisation rate at z<6. The evolution of the volume fraction of ionised hydrogen is not significantly impacted by the inclusion of helium (and is in fact reproduced very well with a simple semi-analytic model), except for a small delay in reionisation when helium is included. The impact of helium on the temperature evolution is larger: at lower redshifts the volume averaged temperature of the IGM is higher. Comparing the simulation results with measurements of the IGM temperature shows that reionisation is mainly driven by sources with a soft spectrum. Contribution from mini-quasars or Pop III stars has to be small at redshifts 6 < z < 9. A significant number of ionising photons is produced by faint, low-mass galaxies.
It seems that the spectral index of the sources has a larger influence on the results than the inclusion of helium. Can the contribution of mini-quasars and pop III stars also be excluded using H-only simulations with harder spectra?
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