Redshift evolution of Lyman continuum escape fraction after JWST

TL;DR

This paper models the evolution of the Lyman continuum escape fraction in galaxies from redshift 0 to 20, linking it to galactic outflows driven by star formation, and compares predictions with observations up to redshift 9.5.

Contribution

The study introduces an Attenuation-Free Model that connects galaxy outflows and star formation rates to the evolution of escape fraction across cosmic time, extending predictions to very high redshifts.

Findings

Escape fraction increases from 0.007 to 0.6 between z=0 and z=20.

Model predictions align with observed escape fractions up to z=9.5.

Explains the decreasing UV spectral slope trend at high redshift.

Abstract

The LyC escape fraction from galaxies, $f_{\rm esc}$, is strongly boosted by galactic outflows. In the Attenuation-Free Model (AFM) accounting for the properties of $z>10$ galaxies, radiation-driven outflows develop once the galaxy specific star formation rate, ${\rm sSFR} \ge {\rm sSFR}^* \approx 25\ {\rm Gyr}^{-1}$. As the cosmic sSFR increases with redshift, so does $f_{\rm esc}(z)$, which, when globally averaged, grows from 0.007 to 0.6 in $0 < z < 20$. We successfully tested the model on specific data sub-samples. Our predictions are consistent with measurements of $f_{\rm esc}$ up to $z=9.5$, and provide a physical explanation for the observed decreasing trend of the mean UV galaxy spectral slope, $\beta$, towards high-$z$.