The Physics of Indirect Estimators of Lyman Continuum Escape and their Application to High-Redshift JWST Galaxies

Understand

Reliable indirect diagnostics of LyC photon escape from galaxies are required to understand which sources were the dominant contributors to reionization.

• While multiple LyC escape fraction ($f_{\rm esc}$) indicators have been proposed to trace favourable conditions for LyC leakage from the interstellar medium of low-redshift ''analog'' galaxies, it remains unclear whether these are applicable at high redshifts where LyC emission cannot be directly observed.
• Using a library of 14,120 mock spectra of star-forming galaxies with redshifts $4.64 \leq z \leq 10$ from the SPHINX$^{20}$ cosmological radiation hydrodynamics simulation, we develop a framework for the physics that leads to high $f_{\rm esc}$.
• We investigate LyC leakage from our galaxies based on the criteria that successful LyC escape diagnostics must i) track a high specific star formation rate, ii) be sensitive to stellar population age in the range $3.5-10~$Myr representing the times when supernova first explode to when LyC production significantly drops, and iii) include a proxy for neutral gas content and gas density in the interstellar medium.