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ABSTRACT Constraining the escape fraction of Lyman Continuum (LyC) photons from high-redshift galaxies is crucial to understanding reionization. Recent observations have demonstrated that various characteristics of the Ly\, emission line correlate with the inferred LyC escape fraction (f βββ^ LyC) of low-redshift galaxies. Using a data set of 9600 mock Ly\, spectra of star-forming galaxies at 4. 64 z 6 from the SPHINX^20 cosmological radiation hydrodynamical simulation, we study the physics controlling the escape of Ly\, and LyC photons. We find that our mock Ly\, observations are representative of high-redshift observations and that typical observational methods tend to overpredict the Ly\, escape fraction (f βββ^ Ly\, ) by as much as 2 dex. We investigate the correlations between f βββ^ LyC and f βββ^ Ly\, , Ly\, equivalent width (W (Ly\, ) ), peak separation (v βββ), central escape fraction (f βββ), and red peak asymmetry (Af^ red). We find that f βββ^ Ly\, and f βββ are good diagnostics for LyC leakage, selecting for galaxies with lower neutral gas densities and less UV attenuation that have recently experienced supernova feedback. In contrast, W (Ly\, ) and v βββ are found to be necessary but insufficient diagnostics, while Af^ red carries little information. Finally, we use stacks of Ly\, , H\, , and F150W mock surface brightness profiles to find that galaxies with high f βββ^ LyC tend to have less extended Ly\, and F150W haloes but larger H\, haloes than their non-leaking counterparts. This confirms that Ly\, spectral profiles and surface brightness morphology can be used to better understand the escape of LyC photons from galaxies during the epoch of reionization.
Choustikov et al. (Fri,) studied this question.