在定常的环行星轨道中通过碰撞尘埃增长的小卫星形成
Satellitesimal Formation via Collisional Dust Growth in Steady Circumplanetary Disks
摘要：
木星周围的冰卫星被认为是在一个环行星盘中形成的。虽然以前的模型侧重于从小卫星开始形成卫星，但小卫星如何从较小的尘埃颗粒形成的问题迄今尚未得到解决。在这项工作中，我们研究的可能性，satellitesimals形成在原地在一个环行星盘。我们计算了表面密度的径向分布和代表性的大小的冰尘埃颗粒，通过相互碰撞和漂移到中央行星在一个稳定的环行磁盘与连续供应的气体和尘埃从母原行星盘。如果尘埃与气体在环行星盘上的吸积率之比$\dot{M}_{\mathrm{d}}/\dot{M}_{\mathrm{g}}$很高，并且湍流强度$α$不太低，则可以克服径向漂移障碍。当$α$较低时，碰撞速度低于临界碎裂速度。综上所述，我们发现通过尘埃凝聚形成小卫星的条件由$\dot{M}_{\mathrm{d}}/\dot{M}_{\mathrm{g}}\ge1$和$10^{-4}\leα<10^{-2}$给出.前一个条件通常难以实现，这表明通过颗粒粘附的原位小卫星形成仅在极端条件下可行。我们还表明，无论是通过多孔聚集体的碰撞生长，也不是通过流动不稳定性的satellitesimal形成是可行的，只要$\dot{M}_{\mathrm{d}}/\dot{M}_{\mathrm{g}}$是低的。
英文摘要：
The icy satellites around Jupiter are considered to have formed in a circumplanetary disk. While previous models focused on the formation of satellites starting from satellitesimals, the question of how satellitesimals form from smaller dust particles has not been addressed so far. In this work, we study the possibility that satellitesimals form in situ in a circumplanetary disk. We calculate the radial distribution of the surface density and representative size of icy dust particles that grow by colliding with each other and drift toward the central planet in a steady circumplanetary disk with a continuous supply of gas and dust from the parent protoplanetary disk. The radial drift barrier is overcome if the ratio of the dust to gas accretion rates onto the circumplanetary disk, $\dot{M}_{\mathrm{d}}/\dot{M}_{\mathrm{g}}$, is high and the strength of turbulence, $α$, is not too low. The collision velocity is lower than the critical velocity of fragmentation when $α$ is low. Taken together, we find that the conditions for satellitesimal formation via dust coagulation are given by $\dot{M}_{\mathrm{d}}/\dot{M}_{\mathrm{g}}\ge1$ and $10^{-4}\leα<10^{-2}$. The former condition is generally difficult to achieve, suggesting that the in-situ satellitesimal formation via particle sticking is viable only under an extreme condition. We also show that neither satellitesimal formation via the collisional growth of porous aggregates nor via streaming instability is viable as long as $\dot{M}_{\mathrm{d}}/\dot{M}_{\mathrm{g}}$ is low.
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