The θ_r−θ_φ space for the streams selected from halo Aq-A (top panels) and Aq-D (bottom panels) shown in previous figures. The angles have been computed using the best fitting spherical NFW potentials, and are centred around the most bound particle in the progenitor, or around a particle closest to the highest density in θ_r−θ_φ space. The colours indicate the energy gradient assuming the spherical NFW potential. The distributions were fitted with straight lines after generously removing particles still bound to the progenitor. The insets show the fitted slope and its error as estimated from bootstrapping 200 times.