Phil Hellary, Richard P. Nelson
(Abridged) We present the results of N-body simulations of planetary systems
formation in radiatively-inefficient disc models, where positive corotation
torques may counter the rapid inward migration of low mass planets driven by
Lindblad torques. The aim of this work is to examine the nature of planetary
systems that arise from oligarchic growth in such discs. We adapt the
commonly-used Mercury-6 symplectic integrator by including simple prescriptions
for planetary migration (types I and II), planetary atmospheres that enhance
the probability of planetesimal accretion by protoplanets, gas accretion onto
forming planetary cores, and gas disc dispersal. We perform a suite of
simulations for a variety of disc models with power-law surface density and
tempera- ture profiles, with a focus on models in which unsaturated corotation
torques can drive outward migration of protoplanets. In some models we account
for the quenching of corotation torques that arises when planetary orbits
become eccentric. Approximately half of our simulations lead to the successful
formation of gas giant planets with a broad range of masses and semimajor axes.
We conclude that convergent migration induced by corotation torques operating
during planet formation can enhance the growth rate of planetary cores, but
these often migrate into the central star because corotation torques saturate.
Outward migration of planetary cores of modest mass can lead to the formation
of gas giant planets at large distances from the central star, similar to those
observed recently through direct imaging surveys. The excitation of planetary
eccentricities through planet-planet scat- tering during oligarchic growth may
quench the effects of corotation torques, however, such that inward migration
is driven by Lindblad torques.
View original:
http://arxiv.org/abs/1112.2997
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