Spatial distribution of the emission of HD 169142 observed with NACO, integrated over the 3.3 µm feature (continuum-subtracted, see details in Sect. 2.3), shown in the upper panel. The inner and outer edge of the gap are shown in with dashed lines. The flux is not computed below 0.168″ and above 0.4″, due to low S/N. The associated azimuthally averaged emission profile is shown in the lower panel. The black solid line is the radial emission profile at 3.3 µm and the grey line is the associated PSF. The grey fill indicates the location of micron- and millimeter-sized grain dust that has been taken from the literature.