On the origin of nitrogen in low-metallicity galaxies - Blue compact galaxies versus damped Ly alpha absorbers

A remarkably small scatter in the N/O ratios for the HII regions in low-met allicity blue compact galaxies (BCG) has been found recently. It lend to th e conclusion that N and O are both produced by massive stars. Conversely, t he N/Si ratios in damped Ly alpha absorbers (DLA, show a large scatter. Thi s result provides support for the time-delay model of nitrogen production i n intermediate-mass stars, nitrogen production in massive stars being not r equired. The goal of this study is to test whether these observational data are compatible with each other and viith the existing ideas on the chemica l evolution of galaxies. We find that it is possible to reconcile the constancy of N/O ratios in low -metallicity BCGs and the scatter of N/Si ratios in DLAs under the followin g three assumptions: I) a significant part of nitrogen is produced by inter mediate-mass stars, 2) star formation in BCGs and DLAs occurs in bursts sep arated by quiescent periods 3) the previous star formation events are respo nsible for measured heavy element abundances of HII regions in BCGs. Since the reality of low N/Si ratios in DLAs is not beyond question, the po ssibility that the nitrogen in low-metallicity BCGs has been produced by ma ssive stars cannot be rejected without additional observations.