Oxygen-enhanced Extremely Metal-poor Damped Lyα Systems: A Signpost of the First Stars?

Abstract

We present precise abundance determinations of two near-pristine damped Ly α systems (DLAs) to assess the nature of the [O/Fe] ratio at [Fe/H] < −3.0 (i.e., <1/1000 of the solar metallicity). Prior observations indicate that the [O/Fe] ratio is consistent with a constant value, [O/Fe] ≃ +0.4, when −3