On the Migration of Protogiant Solid Cores

摘要: The increase of computational resources has recently allowed high resolution, three dimensional calculations planets embedded in gaseous protoplanetary disks. They provide estimates the planet migration timescale that can be compared to analytical predictions. While these predictions result extremely short timescales for cores a few Earth masses, recent numerical have given an unexpected outcome: torque acting on with masses between 5 M_Earth and 20 is considerably smaller than analytic, linear estimate. These findings motivated present work, which investigates existence origin this discrepancy or ``offset'', as we shall call it, by means two calculations. We show offset indeed physical arises from coorbital corotation torque, since (i) it scales disk vortensity gradient, (ii) its asymptotic value depends viscosity, (iii) associated excess horseshoe zone width. corresponds onset non-linearities flow around planet, alter streamline topology mass increases: at low are confined planet's Bondi sphere whereas larger streamlines display classical picture reminiscent restricted body problem, prograde circumplanetary inside ``Roche lobe''. This behavior particular importance sub-critical solid (M <~ 15 M_Earth) thin (H/r <~0.06) Their could significantly slowed down, reversed, disks shallow surface density profiles.