Abundances in damped Lyα galaxies

Abstract

Damped Lyα galaxies provide a sample of young galaxies where chemical abundances can be derived throughout the whole universe with an accuracy comparable to that for the local universe. Despite a large spread in redshift, HI column density and metallicity, DLA galaxies show a remarkable uniformity in the elemental ratios rather suggestive of similar chemical evolution if not of an unique population. These galaxies are characterized by a moderate, if any, enhancement of α-elements over Fepeak elemental abundance with [S/Zn]≈ 0 and [O/Zn]≈ 0.2, rather similarly to the dwarfs galaxies in the Local Group. Nitrogen shows a peculiar behaviour with a bimodal distribution and possibly two plateaux. In particular, the plateau at low N abundances ([N/H] < -3), is not observed in other astrophysical sites and might be evidence for primary N production by massive stars. © 2006 Springer-Verlag Berlin Heidelberg.