Description
Recent JWST observations have revealed remarkably compact morphologies, highly bursty star-formation histories, and puzzling chemical abundances in the earliest galaxies. Due to the unprecedented sensitivity and complexity of these datasets, state-of-the-art cosmological simulations are essential for their accurate interpretation. The THESAN-ZOOM simulations, which integrate high-resolution galaxy formation physics with comprehensive, on-the-fly radiative transfer and a detailed interstellar medium model, provide a powerful laboratory for exploring galaxy evolution from redshifts z = 3 to z = 12. In this talk, I demonstrate that star formation becomes increasingly bursty at higher redshifts, driven primarily by stochastic, rapid gas inflows from the intergalactic medium and frequent galaxy mergers. These intense star formation bursts dramatically influence chemical enrichment, producing extreme and unusual chemical signatures such as pronounced nitrogen enhancement and causing an inversion of the fundamental metallicity relation at early epochs. Furthermore, bursty star formation is closely tied to the morphological evolution of galaxies, inducing repeated cycles of central compaction and subsequent expansion via inside-out quenching. By employing sophisticated forward modeling to produce mock JWST observations, we accurately reproduce the extended Hα emission observed at high redshift. Contrary to interpretations that attribute these extended sizes to gradual inside-out galaxy growth, our analysis reveals that extended Hα regions primarily arise from extreme Lyman continuum photon leakage driven by intense central starbursts. Ultimately, this work underscores the indispensable role of cutting-edge simulations in decoding the complex and often counterintuitive physics shaping early galaxy formation, providing critical insights to inform future observational strategies and theoretical developments.
