The Galactic chemical evolution of oxygen inferred from 3D non-LTE spectral-line-formation calculations

We revisit the Galactic chemical evolution of oxygen, addressing the systematic errors inherent in classical determinations of the oxygen abundance that arise from the use of one-dimensional (1D) hydrostatic model atmospheres and from the assumption of local thermodynamic equilibrium (LTE). We perform detailed 3D non-LTE radiative-transfer calculations for atomic oxygen lines across a grid of 3D hydrodynamic STAGGER model atmospheres for dwarfs and subgiants. We apply our grid of predicted line strengths of the [O I] 630 nm and O I 777 nm lines using accurate stellar parameters from the literature. We infer a steep decay in [O/Fe] for [Fe/H] greater than or similar to -1.0, a plateau [O/Fe] approximate to 0.5 down to [Fe/H] approximate to -2.5, and an increasing trend for [Fe/H] less than or similar to -2.5. Our 3D non-LTE calculations yield overall concordant results from the two oxygen abundance diagnostics.