Behavior of the Ly<i>α</i> 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 (ΔSW 68 ) for an ensemble of damping wing signals. We find that the neutral fraction x H I , quasar lifetime t q , quasar host halo mass M qso , and minimum dark-matter halo mass (that can support star formation) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>M</mml:mi> <mml:mi>min</mml:mi> </mml:msub> </mml:math> significantly impact the median signal. Parameters tied to the reionization topology, like x H I and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>M</mml:mi> <mml:mi>min</mml:mi> </mml:msub> </mml:math> , strongly affect ΔSW 68 , compared with t q . Our findings highlight that quasar damping wings are sensitive to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>M</mml:mi> <mml:mi>min</mml:mi> </mml:msub> </mml:math> , 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.