a) Azimuthally averaged surface density profile for the G16 simulation, Σ(r), at the start (solid black line), after 1500 yr (dashed purple line) and after 2500 yr (dotted green line). The contribution of swept-up ISM at each moment is plotted in the corresponding transparent colour. The vertical arrows in the same colour as the surface density profile indicate the radius of the disc at that moment. b) Same as the left figure, but for the F16 simulation. The initial inner radius at 10 AU is better resolved by Fi than by Gadget2. c) Same as a), but for the reference model without inflow of ISM.