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Galactic Evolution of Nitrogen

G. Israelian·A. Ecuvillon·R. Rebolo·R. Garcia Lopez·P. Bonifacio·P. Molaro
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Abstract

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 A observed at high resolution with various telescopes. We found that [N/Fe] scales with that of iron in the metallicity range -3.1 < [Fe/H] <0 with the slope 0.01+-0.02. 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 HII regions and Damped Ly$α$ systems. This is the first direct comparison of the (N/O) ratios in these objects with those in Galactic stars.

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G. Israelian, A. Ecuvillon, R. Rebolo, R. Garcia Lopez, P. Bonifacio, P. Molaro. 2004-05-04. Galactic Evolution of Nitrogen. https://doi.org/10.1051/0004-6361%3A20047132

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