EDP Sciences
Free access
Volume 397, Number 2, January II 2003
Page(s) 487 - 501
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20021458

A&A 397, 487-501 (2003)
DOI: 10.1051/0004-6361:20021458

On the origin of nitrogen

L. S. Pilyugin1, T. X. Thuan2 and J. M. Vílchez3

1  Main Astronomical Observatory of National Academy of Sciences of Ukraine, 27 Zabolotnogo str., 03680 Kiev, Ukraine
2  Astronomy Department, University of Virginia, Charlottesville, VA 22903, USA
3  Instituto de Astrofísica de Andalucía, Apdo, 3004, 18080 Granada, Spain

(Received 30 May 2002 / Accepted 30 September 2002 )

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.

Key words: galaxies: abundances -- galaxies: ISM -- galaxies: spiral -- galaxies: irregular

Offprint request: L. S. Pilyugin, pilyugin@mao.kiev.ua

SIMBAD Objects

© ESO 2003

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access.

An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account.
    In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.