On the Origin of Nitrogen in Damped Ly-alpha Systems

Abstract

Recent measurements of nitrogen and alpha elements in over 20 damped Ly-alpha systems (DLA) are compared with similar measurements for numerous emission line objects and stars. It is found that the DLA distribution in the N/alpha-alpha/H plane is bimodal, where most sample DLAs fall along the N/alpha plateau defined at low Z by dwarf irregulars, while a small group possesses N/alpha values roughly 0.7 dex less than those on the plateau at similar alpha/H values. We demonstrate with chemical evolution models that a top-heavy or truncated IMF can account for the low N in this second group.

7 pages, in ``CNO in the Universe,'' ASP Conference Series, in press edited by C. Charbonnel, D. Schaerer, and G. Meynet