Outer disk chemical evolution models according to the scheme explained in Sects. 3 and 4, describing the evolution at the solar radius (blue curves) and farther out, starting from a metallicity of −0.6 dex. In all plots, the orange curve is the closed-box chemical evolution model developed in Snaith et al. (2015) and Haywood et al. (2018). In the bottom plot, only the MDFs for stars younger than 9 Gyr (blue curve) and 10 Gyr (red curve) are shown. Both MDFs have been smoothed by a Gaussian kernel of dispersion 0.04 dex.