Description
Recent JWST observations have revolutionised our understanding of chemical evolution and physical conditions in galaxies during the epoch of reionisation, revealing surprisingly compact morphologies, bursty star-formation histories, and intriguing chemical signatures. Accurate interpretation of these observations demands sophisticated theoretical frameworks that self-consistently integrate galaxy evolution, stellar nucleosynthesis, and radiative processes. In this context, the THESAN-ZOOM simulations—a suite of high-resolution cosmological zoom-in simulations that include advanced interstellar medium physics and fully coupled radiative transfer—provide an ideal laboratory to explore galaxy formation and chemical evolution from redshifts z=3 to z=12. In this talk, I present new results from THESAN-ZOOM, highlighting a dramatic increase in the burstiness of star formation towards higher redshifts, driven primarily by stochastic gas inflows from the intergalactic medium and frequent galaxy mergers. These intense starbursts substantially alter chemical enrichment pathways, causing significant deviations from local scaling relations, such as the fundamental metallicity relation, predominantly due to strong inflows of pristine gas onto galaxies experiencing transient episodes of quiescence ("mini-quenching"). Moreover, bursty star formation naturally leads to distinctive chemical phenomena, such as extreme nitrogen enhancement, arising from the preferential ejection of oxygen due to its shorter enrichment timescale during starburst events. Consequently, residual gas is enriched predominantly by delayed yields from intermediate-mass AGB stars. This scenario elegantly explains unusual chemical abundances observed in high-redshift galaxies using standard nucleosynthetic yields, without invoking exotic processes such as the formation of supermassive stars. These findings underscore the critical importance of directly coupling state-of-the-art theoretical models with cutting-edge observational data.
