Improved treatments of the ionizing photon mean free path in semi-numerical simulations of reionization

Efficient and accurate simulations of the reionization epoch are crucial to exploring vast uncharted parameter space that will soon be constrained by measurements 21 cm power spectrum. One these parameters, $R_{\rm max}$, is meant characterize absorption photons residual neutral gas inside ionized regions, but has historically been implemented in a very simplistic fashion acting only as maximum filtering scale. We leverage correspondence between excursion set methods integrated flux from ionizing sources define two physically-motivated prescriptions mean free path smoothly attenuate contribution distant sources. Implementation semi-numerical codes requires modest additional computational effort due fact spatial still performed on scales larger than characteristic distance. find our smoothly-defined more effectively suppress large-scale structures ionization field compared standard max}$ approach, magnitude modulates spectrum much smoother manner. show this suppression significant enough relevant for upcoming observations. Finally, we model plays role regulating history models using max}$.