Star clusters forming in a low-metallicity starburst – rapid self-enrichment by (very) massive stars.

Stellar winds of massive (⁠|$\gtrsim 9\, \mathrm{M_\odot }$|⁠) and very massive (⁠|$\gtrsim 100\, \mathrm{M_\odot }$|⁠) stars may play an important role in the metal-enrichment during the formation of star clusters. With novel high-resolution hydrodynamical griffin -project simulations, we investigate the rapid recycling of stellar wind-material during the formation of massive star clusters up to |$M_\mathrm{cluster}\sim 2\times 10^5\, \mathrm{M_\odot }$| in a low-metallicity dwarf galaxy starburst. The simulation realizes new stars from a stellar initial mass function (IMF) between |$0.08$| and |$\sim 400\, \mathrm{M_\odot }$| and follows stellar winds, radiation and supernova-feedback of single massive stars with evolution tracks. Star clusters form on time-scales less than ∼5 Myr, and their supernova-material is very inefficiently recycled. Stellar wind-material, however, is trapped in massive clusters resulting in the formation of stars self-enriched in Na, Al, and N within only a few Myr. Wind-enriched (second population, 2P) stars can be centrally concentrated in the most massive clusters (⁠|$\gtrsim 10^4\, \mathrm{M_\odot }$|⁠) and the locked wind-material increases approximately as |$M_\mathrm{cluster}^{2}$|⁠. These trends resemble the characteristics of observed 2P stars in globular clusters (GCs). We fit scaling relations to the lognormal distributed wind-mass fractions and extrapolate to possible GC progenitors of |$M_\mathrm{cluster}=10^7\, \mathrm{M_\odot }$| to investigate whether a dominant 2P could form. This can only happen if the IMF is well-sampled, single massive stars produce at least a factor of a few more enriched winds, for example, through a top-heavy IMF, and a significant fraction of the first population (unenriched) stars is lost during cluster evolution. [ABSTRACT FROM AUTHOR]