Abundance Patterns of Heavy Elements in Damped Lyman-Alpha Galaxies

Abstract

We present a quantitative analysis of the abundances of heavy elements in damped Ly-alpha galaxies in the sample of Lu et al. (1996). In particular, we compare the observed gas-phase abundances with those expected when the intrinsic (i.e., nucleosynthetic) pattern is the same as that in either the Sun or in Galactic halo stars and when the depletion pattern is the same as that in the warm Galactic interstellar medium, but with various values of the dust-to-metals ratio. We find that the observations are equally consistent with the solar and halo-star intrinsic patterns and that they favor some depletion, the typical dust-to-metals ratio being 40%-90% of that in the Milky Way today. However, neither intrinsic pattern matches the observations perfectly. For the solar pattern, the discrepancy is mainly with [Mn/Fe], while for the halo-star pattern, the discrepancy is with [Zn/Fe], [Ni/Fe], and possibly [Al/Fe]. Our analysis does not support the claim by Lu et al. that the damped Ly-alpha galaxies have halo-star abundance patterns and no dust depletion.