Bursty star formation, chemical enrichment, and star cluster formation in numerical analogues of GN-z11

Abstract The James Webb Space Telescope reveals anomalous nitrogen enrichment (high ${\rm N/O}$ ratios) in compact, star-forming galaxies, such as GN-z11 at $z\sim 10$. The origin of this chemical signature provides an insight into the early star and galaxy formation processes, yet remains unclear. We performed high-resolution cosmological zoom-in simulations of massive galaxies at high redshift ($z\sim 10$) in rare density peaks, incorporating various chemical evolution channels including stellar winds, core-collapse, Type Ia supernovae, and asymptotic giant branch stars. Our simulations reproduce several key features of high-redshift galaxies: (1) stars form with high efficiencies (${\gt }0.1$) at the center of rare peak halos, creating very compact galaxies similar to GN-z11; (2) high ${\rm N/O}$ ratios emerge during the first 10–20 Myr of intense starburst, before being diluted by core-collapse supernovae; (3) multiple star clusters form in and around the galaxy with high efficiency (${\sim }20\%$), some of which exhibit high ${\rm N/O}$ ratios and sodium-oxygen anti-correlations similar to those observed in local globular clusters. Although our simulations can reproduce the high $\log ({\rm N/O})$ values (up to -0.61, exceeding the solar value by 0.25 dex), they remain below the observational lower limits of GN-z11, indicating room for improvement through additional chemical evolution channels, such as supermassive stars.