Position-velocity (pv) slices for the disc+EPG toy models discussed in Sect. 2.4 and based on the parameters listed in Table 2. For each model we show a pv slice parallel to the major (on the top) and to the minor (on the bottom) axes. The insets in the top-left panels sketch the slice directions. Axis-offset is 2′ in both cases. The slice thickness is 3 spaxels, corresponding to a resolution element. Black contours are spaced by powers of 2, the outermost being at an intensity level of 0.4 mJy beam⁻¹. Red contours show the emission from the disc alone, without the contribution of the EPG.