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arXiv · 2303.07955

N-enhancement in GN-z11: First evidence for supermassive stars nucleosynthesis in proto-globular clusters-like conditions at high redshift ?

C. Charbonnel·D. Schaerer·N. Prantzos·L. Ramírez-Galeano·T. Fragos·A. Kuruvandothi·R. Marques-Chaves·M. Gieles
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Abstract

Unusually high N/O abundance ratios were recently reported for a very compact, intensively star-forming object GN-z11 at $z=10.6$ from JWST/NIRSpec observations. We present an empirical comparison with the C, N, and O abundance ratios in Galactic globular clusters (GCs) over a large metallicity range. We show that hot hydrogen-burning nucleosynthesis within supermassive stars (SMS) formed through runaway collisions can consistently explain the observed abundances ratio in GN-z11 and in GCs. This suggests that a proto-globular cluster hosting a SMS could be at the origin of the strong N-enrichment in GN-z11. Our model predicts the behavior of N/O, C/O, and Ne/O ratios as a function of metallicity, which can be tested if high-$z$ objects similar to GN-z11 are detected with JWST in the future. Further studies and statistics will help differentiate the proto-GC scenario from the Wolf-Rayet scenario that we quantify with a population synthesis model, and shed more light on this peculiar object.

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C. Charbonnel, D. Schaerer, N. Prantzos, L. Ramírez-Galeano, T. Fragos, A. Kuruvandothi, R. Marques-Chaves, M. Gieles. 2023-03-14. N-enhancement in GN-z11: First evidence for supermassive stars nucleosynthesis in proto-globular clusters-like conditions at high redshift ?. https://doi.org/10.1051/0004-6361/202346410

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