Best-fit rotation curve (upper), velocity dispersion profile (middle), and radial motions (lower) of the PN population in M31 (left panel) and M33 (right panel). Black symbols show the results of fitting Eq. (1); green symbols refer to the results when fixing V_exp = 0; red triangles show the H i rotation curve as a comparison with M31 (Corbelli et al. 2010) and M33 (Corbelli & Salucci 2000). Positive values of V_exp correspond to outflowing motions for both galaxies.