Synthetic observations of the PDS 70 models. Disc mass increases from left to right and resolution decreases from top to bottom. For a lower disc mass, the appearance is smooth and symmetric, showing a large gap. At higher disc mass, azimuthal asymmetries appear and additional substructures emerge for higher resolution. Left column (a and c): low-disc-mass model (PDS70 IRR M/5) at t = 70.3 kyr (see vertical line in Fig. 11) and right column (b and d): high-disc-mass model (PDS70 IRR) at the same point in time. Top row (a and b): generated with the same angular resolution as Fig. 10 while only the smaller ALMA antenna configuration was used for the bottom row (c and d), resulting in a larger beam size. The beam size is indicated in the bottom right corner of each image.