GN-z11: Witnessing the formation of second-generation stars and an accreting massive black hole in a massive star cluster

We explore the possibility of the N-rich young proto-galaxy GN-z11, recently observed at z = 10.6 by JWST, being the result of the formation of second generation stars from pristine gas and asymptotic giant branch (AGB) ejecta in a massive globular cluster or nuclear star cluster. We show that a second generation forming out of gas polluted by the ejecta of massive AGB stars and mixed with gas of a standard composition accounts for the unusually large N/O in the GN-z11 spectrum. The timing of the evolution of massive (4-7.5 M_⊙) AGBs also provides a favorable environment for the growth of a central stellar mass black hole to the AGN stage observed in GN-z11. According to our model, the progenitor system was born when the age of the Universe was ≃260 − 380 Myr, well within the bounds of the pre-reionization epoch.