Disk Accretion onto High‐Mass Planets

We analyze the nonlinear, two-dimensional response of a gaseous, viscousprotoplanetary disk to the presence of a planet of one Jupiter mass (1 M_J) andgreater that orbits a 1 solar mass star by using the ZEUS hydrodynamics codewith high resolution near the planet's Roche lobe. The planet is assumed to bein a circular orbit about the central star and is not allowed to migrate. A gapis formed about the orbit of the planet, but there is a nonaxisymmetric flowthrough the gap and onto the planet. The gap partitions the disk into an inner(outer) disk that extends inside (outside) the planet's orbit. For a 1 M_Jplanet and typical disk parameters, the accretion through the gap onto theplanet is highly efficient. For typical disk parameters, the mass doubling timescale is less than 10^5 years, considerably shorter than the disk lifetime.Following shocks near the L1 and L2 Lagrange points, disk material enters theRoche lobe in the form of two gas streams. Shocks occur within the Roche lobeas the gas streams collide, and shocks lead to rapid inflow towards the planetwithin much of planet's Roche lobe. Shocks also propagate in the inner andouter disks that orbit the star. For higher mass planets (of order 6 M_J), theflow rate onto the planet is considerably reduced, which suggests an upper masslimit to planets in the range of 10 M_J. This rate reduction is related to thefact that the gap width increases relative to the Roche (Hill sphere) radiuswith increasing planetary mass. The flow in the gap affects planetarymigration. For the 1 M_J planet case, mass can penetrate from the outer disk tothe inner disk, so that the inner disk is not depleted. The results suggestthat most of the mass in gas giant planets is acquired by flows through gaps.Comment: 28 pages, 11 figures, accepted for publication in Ap