Impacts of stellar wind and supernovae on the star cluster formation: origins of extremely high N/O ratios and multiple stellar populations

Abstract

We study metal enrichment originating from stellar wind and supernovae in low-metallicity clouds by performing three-dimensional radiation hydrodynamics simulations. We find that metals ejected from stellar wind are accumulated, leading to subsequent star formation in the nitrogen-enriched gas. During this early phase, the N/O ratios are similar to observed nitrogen-enriched galaxies (${\rm [N/O]}\gtrsim0.5$). Then, once supernovae occur, the N/O ratios decrease significantly. If the duration of star formation is comparable to the timescale of SNe, the mass fraction of nitrogen-enriched stars reaches half the mass of star clusters. We suggest that the mass of the star cluster needs to exceed $\sim 10^6~M_{\odot}$ to have multiple populations due to stellar wind, considering the condition for massive star cluster formation and the timescales of stellar evolution.