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arXiv 1104.2408astro-ph.EP
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倾斜行星在三维辐射盘中的演化

Evolution of inclined planets in three-dimensional radiative discs

Bertram Bitsch, Willy Kley

摘要:

虽然太阳系中的行星相对于黄道的倾角很小,但越来越多的证据表明,在太阳系外的系统中,倾角可以很大,至少对于近距离的行星来说是这样。改变行星倾角的一个过程是通过行星盘的相互作用。最近的模拟考虑辐射传输表明,迁移和偏心率的演变可以强烈依赖于磁盘的热力学状态。我们扩展了以前的研究,探讨倾斜和偏心轨道上的固定和移动行星的行星盘相互作用。我们还详细分析了盘的热力学性质对嵌入行星轨道演化的影响。原行星盘被模拟为粘性气体,内部产生的耗散通过辐射传输。对于局部等温盘,我们证实了以前的结果,并发现倾斜阻尼和向内迁移的行星核心。当倾角i < 2 H/r时,阻尼是指数的,而当i较大时,di/dt与i^-2成正比。对于辐射盘,行星迁移是非常有限的,只要它们的倾角超过一定的阈值。如果倾斜度被抑制在这个阈值以下,质量高达大约33个地球质量的行星核心开始向外迁移,而较大的核心从一开始就向内迁移。对于所有分析的行星质量,倾角都是阻尼的。在粘性圆盘中,嵌入行星的初始倾角对于所有行星质量都将被阻尼。这种阻尼发生在比迁移时间短的时间尺度上。如果倾角低于某一阈值,则辐射盘中的向外迁移不会受到阻碍。圆形和非倾斜轨道的外移最强。

英文摘要:

While planets in the solar system only have a low inclination with respect to the ecliptic there is mounting evidence that in extrasolar systems the inclination can be very high, at least for close-in planets. One process to alter the inclination of a planet is through planet-disc interactions. Recent simulations considering radiative transport have shown that the evolution of migration and eccentricity can strongly depend on the thermodynamic state of the disc. We extend previous studies to investigate the planet-disc interactions of fixed and moving planets on inclined and eccentric orbits. We also analyse the effect of the disc's thermodynamic properties on the orbital evolution of embedded planets in detail. The protoplanetary disc is modelled as a viscous gas where the internally produced dissipation is transported by radiation. For locally isothermal discs, we confirm previous results and find inclination damping and inward migration for planetary cores. For low inclinations i < 2 H/r, the damping is exponential, while di/dt is proportional to i^-2 for larger i. For radiative discs, the planetary migration is very limited, as long as their inclination exceeds a certain threshold. If the inclination is damped below this threshold, planetary cores with a mass up to approximately 33 Earth masses start to migrate outwards, while larger cores migrate inwards right from the start. The inclination is damped for all analysed planet masses. In a viscous disc an initial inclination of embedded planets will be damped for all planet masses. This damping occurs on timescales that are shorter than the migration time. If the inclination lies beneath a certain threshold, the outward migration in radiative discs is not handicapped. Outward migration is strongest for circular and non-inclined orbits.

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