|Authors:||J. S. Vink 1|
|Affiliations:||(1) Armagh Observatory and Planetarium, Armagh, Northern Ireland|
|Accepted by:||Astronomy & Astrophysics|
Recent studies of high-redshift galaxies such as GN-z11 at z=10.6 with JWST show significant amounts of nitrogen (N) in their spectra, which is unexpected. As this phenomenology appears to extend to gravitionally-lensed galaxies at Cosmic noon such as the Sunburst Arc at z=2.37, as well as Globular Clusters, we suggest the common ingredient to be very massive stars (VMS) with zero-age main sequence (ZAMS) masses in the range 100-1000 Msun. The He II in the Sunburst Arc might also be the result of the disproportionally large contribution of VMS to the total stellar contribution. We analyse the pros and cons of the previous suggestions, including classical Wolf-Rayet (cWR) stars and supermassive stars (SMS), and we conclude that only our VMS alternative ticks all the relevant boxes. We discuss the VMS mass loss history via their peculiar vertical evolution in the HR diagram resulting from a self-regulatory effect of these wind-dominated VMS, and we estimate that the large amounts of N present in star-forming galaxies may indeed result from VMS. We conclude that VMS should be included in population synthesis and chemical evolution models, and moreover that it is critical that this is done self-consistently, as a small error in their mass-loss rates would have dramatic consequences for their stellar evolution, as well as their ionising & chemical feedback.