Transcript Poster - unist

Planet Migration in a Proto-planetary Disk
Hui Zhang 1,3，Chien-Chang Yen 1,2 and Chi Yuan 1
1 Institute
of Astronomy and Astrophysics, Academia Sinica
2 Department of Mathematics, Fu Jen Catholic University
3 Department of Astronomy, NanJing university
Abstract
We present the results of numerical simulations of the migration of a Jovian planet embedded in a self-gravitating proto-planetary disk. The Antares code we have
developed is adopted in the calculations. It is a 2-D Godunov code based on the exact Reimann solution for isothermal or polytropic gas, featured with non-reflecting boundary
conditions and Poisson solver for non-periodic boundary conditions. We use the Cartesian coordinate version of the code to avoid the well-known problem of the inner boundary.
To carry out the calculation, however, a softening length is assigned to the central star. Normally the planet would migrate through all three types of migration phases, from Type I
(embedded) to Type III (presence of horseshoe configuration) to Type II (forming a clear gap). Sometime Type III will re-appear after Type II phase. We find that the rapid
migration in Type I and Type III is associated with the net negative torque within the Roche lobe of the planet, which accounts for more than 60\% of the total torques the planet
experiences. When the gap forms (Type II), hence matter in the lobe is drastically depleted, the planet will migrate slowly. We also notice that the self-gravity of the disk will
change planet's migration rate and enhance its eccentricity. These effects are more pronounced after the gap is well formed. The work is in parts supported by a grant from
National Science Council,Taiwan NSC94-2752-M-001-002-PAE.
High resolution disk evolution
Advantages of Cartesian Frame
•No inner boundary with which we can’t deal perfectly
•Avoid an artificial hole in the center
•More efficient: resolution, computation time
•Uniform resolution all over domain
•Could deal with high q(q=Mp/Ms) case
Migration curves
•Type I,II,III migration
•Migration in high surface density disk
•Migration in self-gravitation disk
High surface density disk evolution
Planet experienced Torque
•Torques from innerdisk are positive
•Torques from outerdisk are negative
•Torques from planet’s Roche lobe
•During Type I,III migration , most torque comes from the planet’s Roche lobe
Eccentricity evolution
•Self-gravitation effect
•High surface density effect
•High ratio(Mplanet/Mstar )
Conclusion
•The high resolution simulations show that planet migration may experience Type III
migration before the gap is well formed
•The rapid migration in Type I and Type III is associated with the net negative torque
within the Roche lobe of the planet
•For a Jupiter mass planet, after the gap is well formed it will be “locked” in an orbit
for a long time, while when we enhance the disk’s surface density it will migrate
inward faster and closer to the central star.
•Effects of self gravitation:Enhance eccentricity; Decrease migration rate ;The higher
surface density the greater self gravitation effects.