Abundance Histories for QSO Absorption-Line Systems

Abstract

Abundance histories for QSO absorption line systems as a function of redshift are presented for all metals lighter than gallium. Coupling various conventional cosmological models with a simple, first--order model for the chemical evolution of the QSO absorption line systems allows transformation of the observed abundance trends in the Galaxy to abundance histories for the gas in QSO absorption line systems. Comparison of the transformed abundance patterns with the zinc to hydrogen [Zn/H] and silicon to hydrogen [Si/H] ratios observed in damped Lyman-$\alpha$ systems finds agreement over more than two orders of magnitude in abundance with a $\Lambda$=0, $\Omega$=0.2 -- 1.0, and $\tau_{\rm {delay}}$=3 Gyr cosmology, where $\tau_{\rm {delay}}$ is the time between the start of the Big Bang and the beginning of galaxy formation. Alternative meanings for the required time delay are explored, along with extensions to the simple first--order model. Predictions are made for the abundance histories of elements not yet observed in QSO absorption line systems.