Frequency distributions computed using the best fitting spherical potentials for our selection of streams from halo Aq-A (top panels) and Aq-D (bottom panels) shown in previous figures. The panels are centred around the same particle, as in Figs. 6 and 7. The distributions were fitted with straight lines after removing generously the bound particles from the progenitor. The colours indicate the energy gradient for the spherical potential. The insets show the fitted slope and estimated errors.