Decoding the Temporal Diagnostics of Lyman Continuum Escape from High-Redshift Galaxies

Abstract

The Epoch of Reionization (EoR) marks a critical phase in cosmic history, driven by the escape of Lyman Continuum (LyC) radiation from early galaxies. At redshifts z > 6, direct observations of LyC are suppressed by the neutral intergalactic medium, making it essential to understand the physical processes that regulate ionizing photon escape. In this work, we investigate these processes using high-resolution radiative transfer calculations applied to cosmological galaxy simulations, focusing on both statistical correlations and time-dependent behavior. We show that the escaping ionizing photon rate strongly tracks the intrinsic production rate, reflecting the most recent underlying star formation activity, which provides the source of the LyC radiation. However, the escape fraction fesc exhibits a delayed response, indicating that photon escape is regulated by the time required for stellar feedback to restructure the surrounding gas to create low-density channels. This demonstrates that LyC escape is governed by a combination of prompt source variability and delayed environmental response. We further show that LyC escape is not steady but exhibits cyclic, feedback-driven variability. Phase-space analysis reveals quasi-periodic trajectories, while cross-correlation measurements confirm a systematic lag between star formation and escape. The characteristic timescales and regularity of these cycles depend on halo mass, with low-mass systems displaying highly stochastic behaviour and more massive systems more coherent cycles. Overall, our results demonstrate that LyC escape is a coupled, time-dependent process shaped by both the source population and the evolving structure of the surrounding medium, providing a physically grounded framework for interpreting the contribution of galaxies to cosmic reionization.