Disk Surface Density Transitions as Protoplanet Traps

Abstract

The tidal torque exerted by a protoplanetary disk with power law surface density and temperature profiles onto an embedded protoplanetary embryo is generally a negative quantity that leads to the embryo inwards migration. Here we investigate how the tidal torque balance is affected at a disk surface density radial jump. The jump has two consequences: • it affects the differential Lindblad torque. In particular if the disk is merely empty on the inner side, the differential Lindblad torque almost amounts to the large negative outer Lindblad torque. • It affects the corotation torque, which is a quantity very sensitive to the local gradient of the disk surface density. In particular if the disk is depleted on the inside and if the jump occurs radially over a few pressure scale-heights, the corotation torque is a positive quantity that is much larger than in a power-law disk. 1