Challenging the LyC-Lyα relation: strong Lyα emitters without LyC leakage at z ~ 2.3

The escape fraction of LyC ionizing radiation fLyCᵉˢᶜ is crucial for understanding reionization, yet impossible to measure at z 5.3. Recently, studies have focused on calibrating indirect indicators of fLyCᵉˢᶜ at z ~ 0.3, finding that Lyα is closely linked to it. What is still unclear is whether the LyC - Lyα relation evolves with redshift, and if Lyα is truly applicable as an fLyCᵉˢᶜ indicator during the reionization epoch. In this study, we investigate seven -21 MUV -19 gravitationally lensed galaxies from the BELLS GALLERY survey at z ~ 2.3. Our targets have rest-frame Lyα equivalent widths ranging from 10 {A} to 100 {A} and low dust content (-2.5 β -1.9), both indicative of high LyC escape. Surprisingly, direct estimates of fLyCᵉˢᶜ using Hubble Space Telescope imaging with F275W and F225W reveal that our targets are not LyC emitters, with absolute fLyCᵉˢᶜ 6.5% at 3σ significance (with two sources having absolute fLyCᵉˢᶜ(3σ) 10% and 16%). The low fLyCᵉˢᶜ, coupled with the high Lyα escape fraction and equivalent width could potentially be attributed to the redshift evolution of the neutral hydrogen column density and dust content. Our results challenge previous studies based on local samples, suggesting that the extrapolation of z ~ 0 Lyα-based LyC indirect estimators into the reionization epoch might not be correct.