Low and intermediate mass star yields

II. The evolution of nitrogen abundances

¹ Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049 Cantoblanco, Spain e-mail: marta.gavilan@uam.es
² Departamento de Investigación Básica, C.I.E.M.A.T., Avda. Complutense 22, 28040 Madrid, Spain e-mail: mercedes.molla@ciemat.es
³ Department of Mathematics and Physics, Alfred State College, Alfred, NY 14802, USA e-mail: BuellJF@alfredstate.edu

Received: 7 June 2005
Accepted: 25 November 2005

Abstract

Aims.We analyze the impact on the Galactic nitrogen abundances with a new set of low and intermediate mass star yields. These yields contain a significant yield of primary nitrogen from intermediate mass stars.

Methods.We use these yields as an input for a galactic chemical evolution model and study the nitrogen abundances in the halo and in the disc, and compare them with models obtained using other yield sets and with a large amount of observational data.

Results.We find that with these new yields our model reproduces the observed trends adequately. In particular, these yields solve the historical problem of nitrogen evolution, giving the right level of relative abundance N/O by producing a primary component in intermediate mass stars. Moreover, using different evolutionary rates for each radial region of the Galaxy, we can explain the observed N dispersion.