Title: Ionizing Radiation, Nebular Emission, and Lyman-alpha Feedback in the High-Redshift Universe
Abstract: I will present recent results and developments from the THESAN Project, a suite of cosmological radiation-hydrodynamic simulations designed to connect high-redshift galaxy formation to the large-scale statistics and topology of the Epoch of Reionization. A central focus of the talk will be the THESAN-ZOOM simulations, which resolve individual z > 3 galaxies with a multi-phase interstellar medium and local stellar feedback, enabling self-consistent predictions for the production, propagation, and escape of Lyman-continuum (LyC) and Lyman-alpha (Lyα) radiation from the ISM into the CGM and beyond. Leveraging the COLT Monte Carlo radiative transfer framework, I will discuss diagnostics that link gas morphology and kinematics to the ionizing escape fraction, and how these galaxy-scale trends connect back to the ionizing photon budget inferred from larger-volume THESAN runs. I will also highlight a major JWST-motivated update to COLT for forward modeling nebular line and continuum emission, including a thermally coupled equilibrium solver and expanded atomic physics that improve UV-IR line predictions across cosmic time. Finally, I will discuss our new progress on Lyα radiation pressure, including the first 2D Lyα radiation-hydrodynamics simulations with the LYDION code, which indicate that Lyα feedback can dominate in sufficiently dust-poor environments, with broad implications for star formation and reionization at Cosmic Dawn.