Abundances in Spiral Galaxies: Evidence for Primary Nitrogen Production
Abstract
We present the results of nitrogen and oxygen abundance measurements for 185 H II regions spanning a range of radii in 13 spiral galaxies. As expected, the nitrogen-to-oxygen ratio increases linearly with the oxygen abundance for high-metallicity H II regions, indicating that nitrogen is predominantly a secondary element. However, the nitrogen-to-oxygen ratio plateaus for oxygen abundances less than 1/3 solar [12 + log (O/H) < 8.45], as is also seen in low-metallicity dwarf galaxies. This result suggests that the observed trend in dwarf galaxies is not due to the outflow of enriched material in a shallow gravitational potential. While the effects of the infall of pristine material and delayed nitrogen delivery are still unconstrained, nitrogen does appear to have both a primary and a secondary component at low metallicities in all types of galaxies.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1998
- DOI:
- 10.1086/311263
- arXiv:
- arXiv:astro-ph/9802147
- Bibcode:
- 1998ApJ...497L...1V
- Keywords:
-
- GALAXIES: ABUNDANCES;
- GALAXIES: ISM;
- GALAXIES: SPIRAL;
- Galaxies: Abundances;
- Galaxies: ISM;
- Galaxies: Spiral;
- Astrophysics
- E-Print:
- 10 pages, 2 figures, uses AASTex and psfig. Accepted to ApJL