The nitrogen-to-oxygen ratio in galaxies and its implications for the origin of nitrogen.
Abstract
We re-examine the available data on nitrogen and oxygen abundances deduced from the spectra of giant H II regions in external galaxies. If account is taken of the likely differences in temperature between the [O II] and [O III] ionization zones, the derived N/O ratios as a function of O/H can consistently be explained by models in which nitrogen has both a (delayed) primary and a secondary component relative to oxygen, with the secondary component dominating at high abundance. There is also some evidence that the secondary component is delayed (by perhaps 2 x 10^9^ yr), and that there is some spread in the ages of the discs of late-type spirals.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- November 1993
- DOI:
- 10.1093/mnras/265.1.199
- Bibcode:
- 1993MNRAS.265..199V