Secular Gravitational Instability of Drifting Dust in Protoplanetary Disks: Formation of Dusty Rings without Significant Gas Substructures
Secular Gravitational Instability of Drifting Dust in Protoplanetary Disks: Formation of Dusty Rings without Significant Gas Substructures
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DOI：
10.3847/1538-4357/abad36
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发表时间：
2020-08
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影响因子：
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通讯作者：
Ryosuke T. Tominaga;Sanemichi Z. Takahashi;S. Inutsuka
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作者：
Ryosuke T. Tominaga;Sanemichi Z. Takahashi;S. Inutsuka
长期引力不稳定性（GI）是在原行星盘中产生环形子结构和星子的一种有前景的机制。我们对具有向内漂移的尘埃颗粒的径向延伸圆盘中的长期 GI 进行数值模拟。结果表明，即使存在灰尘扩散，尘埃环也会在尘埃颗粒向内移动时通过长期 GI 形成，并且灰尘表面密度会增加 10 倍。一旦长期 GI 发展成非线性状态，所得环的总质量可能会占尘埃盘质量的很大一部分。这样，大量飘浮的尘埃颗粒就可以被收集在尘埃环中，并储存起来以供星子形成。与显着的尘埃子结构的出现相反，长期的 GI 不会产生显着的气体子结构。这一结果表明，对圆盘中平面附近气体密度分布的观察使我们能够区分在观察到的圆盘中创建环形子结构的机制。一旦进入对长期 GI 稳定的内部区域，所产生的环就开始衰减。由于环隙对比度平滑减小，因此即使在稳定区域也可能观察到环。我们还讨论了非线性增长的可能结果，并指出长期 GI 显着发达的区域可能在尘埃连续发射中表现为间隙状子结构，因为尘埃生长成更大的固体和星子形成降低了总发射率。
Secular gravitational instability (GI) is one promising mechanism for creating annular substructures and planetesimals in protoplanetary disks. We perform numerical simulations of secular GI in a radially extended disk with inwardly drifting dust grains. The results show that, even in the presence of dust diffusion, dust rings form via secular GI while the dust grains are moving inward, and the dust surface density increases by a factor of 10. Once secular GI develops into a nonlinear regime, the total mass of the resultant rings can be a significant fraction of the dust disk mass. In this way, a large amount of drifting dust grains can be collected in the dusty rings and stored for planetesimal formation. In contrast to the emergence of remarkable dust substructures, secular GI does not create significant gas substructures. This result indicates that observations of a gas density profile near the disk midplane enable us to distinguish the mechanisms for creating the annular substructures in the observed disks. The resultant rings start decaying once they enter the inner region stable to secular GI. Because the ring-gap contrast smoothly decreases, it seems possible that the rings are observed even in the stable region. We also discuss the likely outcome of the nonlinear growth and indicate the possibility that a significantly developed region of secular GI may appear as a gap-like substructure in dust continuum emission as dust growth into larger solid bodies and planetesimal formation reduce the total emissivity.