The N/O evolution on galaxies:the role played by the star formation history

We study the evolution of nitrogen resulting from a set of spiral and irregular galaxy models computed for a large number of input mass radial distributions and with various star formation efficiencies. We show that our models produce a nitrogen abundance evolution in good agreement with the observational data. In particular, low N/O values for high-redshift objects, such as those obtained for Damped Lyman Alpha galaxies can be obtained with our models simultaneously to higher and constant values of N/O as those observed for irregular and dwarf galaxies, at the same low oxygen abundances $\rm 12+log(O/H) \sim 7$ dex. The differences in the star formation histories of the regions and galaxies modeled are essential to reproduce the observational data in the N/O-O/H plane