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

Stellar winds of massive (greater than or similar to 9 M-circle dot) and very massive (greater than or similar to 100 M-circle dot) 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-cluster similar to 2 x 10(5) M-circle dot in a low-metallicity dwarf galaxy starburst. The simulation realizes new stars from a stellar initial mass function (IMF) between 0.08 and similar to 400 M-circle dot and follows stellar winds, radiation and supernova-feedback of single massive stars with evolution tracks. Star clusters form on time-scales less than similar to 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 (greater than or similar to 10(4) M-circle dot) and the locked wind-material increases approximately as M-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-cluster = 10(7) M-circle dot 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.