Open AccessNova nucleosynthesis and Galactic evolution of the CNO isotopes
Author(s) -
Romano Donatella,
Matteucci Francesca
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2003.06526.x
Subject(s) - physics , astrophysics , nucleosynthesis , stars , stellar nucleosynthesis , galaxy , astronomy , initial mass function , star formation
In this paper we study the role played both by novae and single stars in enriching the interstellar medium of the Galaxy with CNO group nuclei, in the framework of a detailed successful model for the chemical evolution of both the Galactic halo and disc. First, we consider only the nucleosynthesis from single low‐mass, intermediate‐mass and massive stars. In particular, the nucleosynthesis prescriptions in the framework of the adopted model are such that (i) low‐ and intermediate‐mass stars are responsible for the production of most of the Galactic 12 C and 14 N; (ii) massive stars produce the bulk of the Galactic 16 O; (iii) 13 C and 17 O originate mostly in intermediate‐mass stars, with only a minor contribution from low‐mass and massive stars. In this context, we show that the behaviour of the 12 C/ 13 C, 14 N/ 15 N and 16 O/ 17 O isotopic ratios, as inferred from observations, can be explained only allowing for a substantial revision of the available stellar yields. On the other hand, the introduction of nova nucleosynthesis allows us to better explain the temporal evolution of the CNO isotopic ratios in the solar neighbourhood as well as their trends across the Galactic disc. Once all the nucleosynthesis sources of CNO elements are taken into account, we conclude that 13 C, 15 N and 17 O are likely to have both a primary and a secondary origin, in contrast to previous beliefs. We show that, when adopting the most recent 17 O yields from intermediate‐mass stars published in the literature so far, we still get a too large solar abundance for this element, a problem already encountered in the past by other authors using different yield sets. Therefore, we conclude that in computing the 17 O yields from intermediate‐mass stars some considerable sink of 17 O is probably neglected. The situation for 15 N is less clear than that for 13 C and 17 O, mainly due to contradictory observational findings. However, a stellar factory restoring 15 N on quite long time‐scales seems to be needed in order to reproduce the observed positive gradient of 14 N/ 15 N across the disc, and novae are, at present, the best candidates for this factory. Given the uncertainties still present in the computation of theoretical stellar yields, our results can be used to put constraints on stellar evolution and nucleosynthesis models.