Absolute distribution of the radial velocities, v_R, for stars in eight regions defined in Fig. 6 (see Sect. 3.2). In all panels, velocities are in units of 100 km s⁻¹. The number of stars in each region is given at the upper-left of each panel. The 1σ uncertainties (coloured, shaded regions) were estimated by taking into account both the statistical uncertainty, through 1000 bootstrapped realisations, and the individual uncertainties propagated from the observables.