Simulated images of the disc-planet models used in this study for the case of an embedded planet orbiting at 20   AU (white dot). Left to right columns correspond to polarised-intensity (PI) ZIMPOL images in the R-band (0.65   μm), PI HiCIAO images in H-band (1.6   μm) and intensity (I) ALMA images at 850   μm. Top, middle and bottom rows show images obtained for planet masses of M_p =  [1,9,15]    M_Jup respectively. All images in the same band (column) share the colour scale, although the cases of 9 and 15   M_Jup in R and H polarised-intensity have been multiplied by a small factor to enhance the contrast. See Sect. 2 for details on how the models/images were generated.