2002/10/10 by L. S. Pilyugin, T. X. Thuan, J. M. Vı́lchez +1 · 2 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Disc #Dwarf galaxy #Elliptical galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy group #Irregular galaxy #Lenticular galaxy #Metallicity #Milky Way #Physics #Spiral galaxy #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20021458
published as Astron.Astrophys.397:487-502,2003 · 16 pages, 11 figures, accepted for publication in Astronomy and Astrophysics
arxiv created 2002/10/10 · openalex publication_date 2002/12/17 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The problem of the origin of nitrogen is considered within the framework of an empirical approach. The oxygen abundances and nitrogen to oxygen abundances ratios are derived in H ii regions of a number of spiral galaxies through the recently suggested P–method using more than six hundred published spectra. The N/O–O/H diagram for H ii regions in irregular and spiral galaxies is constructed. It is found that the N/O values in H ii regions of spiral galaxies of early morphological types are higher than those in H ii regions with the same metallicity in spiral galaxies of late morphological types. This suggests a long-time-delayed contribution to the nitrogen production. The N/O ratio of a galaxy can then be used as an indicator of the time that has elapsed since the bulk of star formation occurred, or in other words of the nominal “age” of the galaxy as suggested by Edmunds & Pagel more than twenty years ago. The scatter in N/O values at a given O/H can be naturally explained by differences in star formation histories in galaxies. While low-metallicity dwarf galaxies with low N/O do not contain an appreciable amount of old stars, low-metallicity dwarf galaxies with an appreciable fraction of old stars have high N/O. Consideration of planetary nebulae in the Small Magellanic Cloud and in the Milky Way Galaxy suggests that the contribution of low-mass stars to the nitrogen production is significant, confirming the conclusion that there is a long-time-delayed contribution to the nitrogen production.