Mean azimuthal velocity of the representative groups in the R − ϕ projection, for |Z|< 0.2 kpc. The contours of regions with the same velocity are shown for clarity (in white). The Arcturus, Bobylev, and Hercules moving groups present a constant slope in the variation of azimuthal velocity along azimuth, whereas the Horn, Sirius, and Arch/Hat moving groups present an axisymmetrical behaviour of the azimuthal velocity along azimuth.