Time evolution of rest-mass density (upper half panels) and axial velocity (lower half panels, mirror of the upper panels) for S1 in 2D. The black lines give the contour of the jet-mass fraction for the tracer value f = 0.5. The jet is propagating from the left to the right. Top left: t ≈ 1600 yr from the start of the simulation; top right: t ≈ 2300 yr; bottom left: t ≈ 3000 yr; bottom right: t ≈ 3800 yr.