Surface densities from eight simulations for two different values of q. The white circles enclose the region r < 2 a of the disk, with a the binary separation. From left to right, the panels show a binary far from the gap-forming regime, a binary with parameters in the vicinity of the gap-forming regime that does not form a gap in the disk, a binary that begins to excavate a gap on the disk, and a binary that excavates a gap in the disk. The geometry of the density perturbation is spiral for the simulations within the gap-forming regime ((c), (d), (g), and (h)) and for the simulation in the vicinity of the gap-forming regime ((b) and (f)). In contrast, we can see that for the simulation that is far from the gap-forming regime, the density perturbation has an ellipsoidal geometry for q = 1 and a pear shape for q = 0.1 [(a) and (e)].