Collapse of dust parcels in the Std-med model. Top left set of three panels: very early time step in the collapse. The colour of each point is the same as in Fig. 4. Each set of three panels shows the same time step at three different lengths scales. The right panel shows the length scales relevant for the embedded disk. The second, third, and forth set represent the simulation at 0.25, 0.5, and 0.75 t_acc respectively. As the disk builds, some of the dust drifts radially inward, some is advected outward with the growing gas disk, and missing dust is replenished by newly infalling dust. For comparison, the black line shows an estimate of the location of the gas rarefaction wave defined by x = 1.