ZIMPOL polarized light brightness profiles. a) Radial profile in the inner 0.3′′. The location of the abrupt decrement along the near side axis and the spiral arm bump along the far side axis are highlighted by the horizontal dashed lines. b) Radial profile along the SE axis compared to the same from the NACO dataset. Each profile is normalized to the respective peak intensity. The predicted radial location of HD 100546c is indicated by the vertical brown area. The angular resolution of the three datasets is shown by the horizontal lines. c) Projected azimuthal profile of the inner rim (at r = 0.15″ for i = 42°). Angles from north to east. The emission from the four different quadrants is shown with different colors. d) Projected azimuthal profile at the predicted radial location of HD 100546b (see red ellipse in Fig. 1c) compared with the same from the NACO dataset. Each profile is normalized to the respective peak intensity. The azimuthal location of b is indicated by the vertical brown region. The vertical dashed lines define the four quadrants as in c). In the lower space, the same normalized brightness distribution from the SPHERE U_φ image is shown (note the different y-axis scale therein). All errors are given at 3σ level as described in Sect. 3.1.