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Newborn super star clusters at Cosmic Noon seen through gravitational lensing

Liang Dai, UC Berkeley
Tuesday, December 6, 2022 - 3:00pm
PAT C-421

Super star clusters with masses > 1e6 Msun are thought to be progenitors of globular clusters (GCs). Their births however are seldomly seen in the local Universe. The puzzle of chemically peculiar populations found in most globular clusters implies that much is to be understood about what happens in the immediate environment of young super star clusters that host a large number of massive stars. We present a joint photometric and spectroscopic study of a highly magnified, LyC-leaking super star cluster candidate with a mass >1e7 Msun and an age ~3–4 Myr, in a lensed Cosmic Noon galaxy. We determine physical and geometrical parameters describing the star cluster and its surrounding photoionization nebula, and measure nebular abundances of several chemical elements. We found dense, highly-pressurized photoionized clouds at just ~ 10 pc that are severely enriched with nitrogen. We theorize that these dense clouds originate from slow massive star ejecta that are efficiently retained in the cluster's gravitational potential. This may have implications for the origin of chemically peculiar stars in globular clusters. Our findings encourage better understanding of the interplay between radiation, gas dynamics and gravity in the densest star-forming systems in the Universe.