Snapshots of the surface density for model M9-3 showing the disc at different times: prior (panels a and b), during (c and d), and after (e and f) a migration jump. The current orbits of the two planets are marked by the dotted white ellipses and the planetary Hill spheres are indicated by the small circles. Coordinate labels show the position in au. The snapshots are rotated to have the outer planet fixed on the horizontal axis to the right of the origin. Time inside the simulation is shown in the upper right corner. The time of a particular snapshot in the time-line of the simulation can be located on the annotated vertical lines in Fig. 4. For synthetic observations of the snapshots, see Fig. 10.