Variation of the spherical velocity components with distance from the plane, |Z|, for ∼34 000 candidate halo red giants from the solar cylinder with measured radial velocities and [Fe/H] < −1.2. Triangles show the mean values in bins of |Z| and the thick dashed lines show the ±2σ envelope around means, where σ is the standard deviation for each bin (i.e., velocity dispersion). The dot-dashed lines represent the halo velocity ellipsoid model described in Sect. 2.2.2.