Velocity dispersion of the cylindrical Galactocentric components V_r, V_ϕ, and V_z for the HQS. The blue dots and error bars stand for the standard deviations of the velocities and their uncertainties obtained by fitting a Gaussian on each component of the velocities in each of the seven age bins of Table 3, the oldest age bin having an upper limit of 2.5 Gyr. The x value of the blue dots is the median value of the corresponding age bin. The black line shows the best-fit power law obtained using an ML on each cluster of the HQS younger than 2.5 Gyr, and the grey lines represent the uncertainties of the fits.