Behavior of the Lyα Damping Wings as a Function of Reionization Topology

Abstract

The damping wing signatures in high-redshift quasars have proven instrumental in studying the epoch of reionization. With the upcoming Euclid mission set to discover many more quasars, it is crucial to explore what this new set of quasars might reveal not only about the reionization history, but also about its topology. The topology should influence the shape and variation of quasar-damping wing signals across sightlines. We use 21cmFAST to generate patchy reionization models in cosmological volumes with diverse astrophysical parameters for the ionizing sources. We examine the median and the sightline-to-sightline variation (ΔSW68) for an ensemble of damping wing signals. We find that the neutral fraction xH I, quasar lifetime tq, quasar host halo mass Mqso, and minimum dark-matter halo mass (that can support star formation) M min significantly impact the median signal. Parameters tied to the reionization topology, like xH I and M min , strongly affect ΔSW68, compared with tq. Our findings highlight that quasar damping wings are sensitive to M min , a key variable linking reionization topology, history, and feedback processes. We also explore the convergence of damping wing signals and ionized bubble sizes with box size. We present a suite of models to assess the ability of future quasar samples to constrain astrophysical model parameters and the additional systematic uncertainty on the neutral fraction incurred when fixed to a single fiducial value. © 2025. The Author(s). Published by the American Astronomical Society.