R. B. C. Henry, Jason X. Prochaska
Published 2002-11-22Version 1
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.
Comments: 7 pages, in ``CNO in the Universe,'' ASP Conference Series, in press edited by C. Charbonnel, D. Schaerer, and G. Meynet
Molecular Hydrogen in Damped Ly-alpha Systems: Spatial Distribution
Optical monitoring of the z=4.40 quasar Q 2203+292
Molecular hydrogen in damped Ly-alpha systems: clues to interstellar physics at high-redshift
