Radial-velocity estimates from He IIλ5411.5 (left-hand panel) for 270 early-type stars compared with estimates from the Hα and N II λ6583.45 nebular lines superimposed on the spectra (central and right-hand panels, respectively). The colour of each hexagon indicates the median velocity of the sources in that area and follows the same scale as in Fig. 10. The black dashed line in each panel is the rotational axis proposed by Hénault-Brunet et al. (2012b).