Volume 421, Number 2, July II 2004
|Page(s)||649 - 658|
|Section||Galactic structure, stellar clusters, and populations|
|Published online||22 June 2004|
Galactic evolution of nitrogen
Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
2 Consejo Superior de Investigaciones Científcas, Spain
3 Departamento de Astrofísica, Universidad de La Laguna, Av. Astrofísico Francisco Sánchez s/n, 38206 La Laguna, Tenerife, Spain
4 Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
Corresponding author: G. Israelian, firstname.lastname@example.org
Accepted: 23 March 2004
We present detailed spectroscopic analysis of nitrogen abundances in 31 unevolved metal-poor stars analysed by spectral synthesis of the near-UV NH band at 3360 Å observed at high resolution with various telescopes. We found that [N/Fe] scales with that of iron in the metallicity range with the slope . Furthermore, we derive uniform and accurate (N/O) ratios using oxygen abundances from near-UV OH lines obtained in our previous studies. We find that a primary component of nitrogen is required to explain the observations. The NH lines are discovered in the VLT/UVES spectra of the very metal-poor subdwarfs G64-12 and LP815-43 indicating that these stars are N rich. The results are compared with theoretical models and observations of extragalactic H II regions and Damped Lyα systems. This is the first direct comparison of the (N/O) ratios in these objects with those in Galactic stars.
Key words: stars: abundances / galaxies: abundances
© ESO, 2004
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