Reconstruction of the source plane in each velocity bin as described in the text. The velocity bins are color-coded, following the color bar to the right and as represented in Fig. 2. The circles represent the size of the reconstructed emission in each velocity bin, defined by the half-light radius (see text). The color-coded central dots show the reconstructed source position at the respective velocity bin. The dotted black line shows the lensing caustic curve from the lens model of Spilker et al. (2016).