a) [Ni/Fe] – [Na/Fe] for the sample where the solid line marks the approximate separation between the low-α and high-α halo populations discovered by Nissen & Schuster (2010). Stars that have a total space velocity greater than V_TOT > 180      km   s^-1 have been marked by open blue circles if located on the upper-right side of the dividing line, and by solid red circles if located on the lower-left side. b) [Ti/Fe] – [Fe/H] for the sample with the same coding as in a). c) Toomre diagram with the same coding as in a). The curved line marks V_TOT = 180      km   s^-1. d) Cumulative distributions of V_TOT: dashed red line represents the red stars in a)–c), solid blue line the blue stars in a)–c), and dotted blue line the blue stars in a)–c) but only including stars with V_TOT > 200      km   s^-1.