Left: spatial distribution of the four following masks: in blue, in green, in orange, and in red. The percentages in the legend list the fraction of the surface contained in the different masks. Right: flux integrated over the masks as a function of velocity. The spectrum of different colors illustrates the evolution of the flux for the same line as a function of the mask used: all pixels observed in black, all pixels with in blue, all pixels with in green, all pixels with in orange, and all pixels with in red.