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

TL;DR

This study uses high-resolution cosmological simulations to explore the origins of nitrogen enrichment and star cluster formation in early galaxies like GN-z11, revealing insights into their chemical signatures and star formation processes.

Contribution

The paper introduces detailed simulations of high-redshift galaxies that reproduce key features of GN-z11, including nitrogen enrichment and star cluster formation, highlighting the role of early starbursts.

Findings

High star formation efficiencies produce compact galaxies similar to GN-z11.

High N/O ratios develop early during starbursts before dilution by supernovae.

Multiple star clusters form with high efficiency, some showing chemical signatures akin to globular clusters.

Abstract

The James Webb Space Telescope reveals anomalous nitrogen enrichment (high N/O ratios) in compact, star-forming galaxies, such as GN-z11 at $z\sim10$. 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 ($z\sim10$) 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 ($>0.1$) at the center of rare peak halos, creating very compact galaxies similar to GN-z11; (2) high N/O ratios emerge during the first 10-20 Myr of intense starburst, before being diluted by CCSNe; (3) multiple star clusters form in and around the galaxy with high efficiency ($\sim20\%$), some of which exhibit high N/O ratios and sodium-oxygen anti-correlations similar to those observed in local globular clusters. Although our simulations can reproduce the high log(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.