Relationship between scatter in [Fe/H] and [Fe/H] radial birth gradient. Each point represents a different age bin, colored from youngest (blue) to oldest (yellow). The grey line is the line of best-fit. The correlation between ∇[Fe/H](τ) and $\mathrm{Range}\stackrel{\sim }{[\mathrm{Fe}/\mathrm{H}]}(\mathrm{age})$ is given in the bottom left of each panel. The red font indicates the galaxies analysed in Figure 5.