Absolute residual histograms (with Poisson error bars) for stars with τ < 2 Gyr in the smallest (panel (a), cyan) and largest (panel (b), red) a_R bins. The dashed curves show the model p_tot for each value of a_R (in corresponding colors), using m_R = −0.0678 dex kpc^–1 and the fitted σ_tot value for this age bin. The shaded regions show the range of model distributions obtained by varying the fitted σ_tot by ﹩\pm 1{\sigma }_{{\sigma }_{{\rm{tot}}}}﹩.