Type I Migration in a Nonisothermal Protoplanetary Disk

Abstract

We calculate rates of type I migration of protoplanets in a nonisothermal three-dimensional protoplanetary disk, building on planet-disk models developed in previous work. We find that including the vertical thickness of the disk results in a decrease in the type I migration rate by a factor of ~2 from that of a two-dimensional disk. The vertical temperature variation has only a modest effect on migration rates, since the torques at the midplane are weighted heavily because both the density and the perturbing potential are maximized at the midplane. However, temperature perturbations resulting from shadowing and illumination at the disk's surface can decrease the migration rate by up to another factor of 2 for planets at the gap-opening threshold at distances for which viscous heating is minimal. This would help to resolve the timescale mismatch between the standard core-accretion scenario for planet formation and the survival of planets and could help explain some of the rich diversity of planetary systems already observed.