Upper panels: surface brightness profiles (gray lines) extracted from the 12 sectors centered on MF of the three images of Fig. 1, representative of the classes: VR (left panel), R (central panel), and IR (right panel). The thick solid lines show the mean profile. The median profile is not shown for clarity. Lower panels: azimuthal scatter profiles derived as in Eq. (2) and computed with respect to the median profile and centered on MF, , for clarity simply referred to as σ_A in the plot.