Top panel: fraction of counter-rotating stars in [Fe/H]–[Mg/Fe] plane. The pixel size is 0.152 × 0.044, and only pixels containing more than ten stars are shown. Middle panel: fraction of counter-rotating stars as a function of their [Mg/Fe] ratio. In each panel, coloured curves indicate stars in specific bins of [Fe/H], as indicated in the legend. The black curves show the corresponding relation for the total sample. Bottom panel: fraction of counter-rotating stars as a function of their [Fe/H] ratio. In each panel, coloured curves indicate stars binned by their [Mg/Fe] values (see legend in upper left-hand corner of the panel). The uncertainties were estimated using a bootstrapping procedure as previously described. Middle and bottom panels: only bins containing more than ten stars are shown.