High N/O ratio at high redshift as a result of a strong burst of star formation and differential galactic winds

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Abstract
Context. Recent observations by JWST have revealed supersolar 14N abundances in galaxies at very high redshift. On the other hand, these galaxies show subsolar metallicity. The observed N/O ratios are difficult to reproduce in the framework of chemical evolution models for the Milky Way. Aims. Our aim is to reproduce these high N/O ratios with chemical evolution models, assuming different histories of star formation triggering galactic winds, coupled with detailed nucleosynthesis prescriptions for 14N, 12C, 16O, and 56Fe. Methods. We computed several models for small galaxies (109−1010 M⊙) with a high star formation efficiency and strong galactic winds. These winds are assumed to be differential, mainly carrying out the products of the explosion of core-collapse supernovae. Results. We find that only models with high star formation rates, a normal initial mass function, and differential galactic winds can reproduce the observed chemical abundances. We also find that, with the same assumptions about star formation and galactic winds, but with a very rapid formation resulting from fast gas infall, we can also reproduce the estimated ages of these objects. We find no necessity to invoke peculiar nucleosynthesis from population III stars, very massive stars, and supermassive stars.
Funding Information
  • Ministero dell'Università e della Ricerca (2022X4TM3H)
  • Istituto Nazionale di Astrofisica (1.05.12.06.05 Theory Grant)
  • Ministero dell'Università e della Ricerca (2022ARWP9C)
  • Science and Technology Facilities Council
  • European Research Council (Advanced Grant 695671)
  • UK Research and Innovation (Frontier Research grant RISEandFALL)
  • Royal Society

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