arXiv 1601.059452016-01-22astro-ph.EP

由二维原行星盘中涡旋触发的尘埃捕获和长寿命密度增强

Dust capture and long-lived density enhancements triggered by vortices in 2D protoplanetary disks

Clément Surville, Lucio Mayer, Douglas N. C. Lin

备注：: Preprint version, submitted to the Astrophysical Journal. Due to size constraints on ArXiv, some plots are at low resolution JPEGs
DOI：: 10.3847/0004-637X/831/1/82

摘要：

我们研究尘埃捕获的旋涡和其长期的后果，在全球两种流体无粘磁盘模拟使用一个新的极坐标网格代码RoSSBi。我们进行了迄今为止最长的积分，几百个磁盘轨道，在全球模拟磁盘的尘埃，即2048x4096网格点的最高分辨率。这使得研究尘埃演化远远超出涡旋耗散。我们改变了很大范围的参数，最值得注意的是初始设置中的粉尘与气体的比率在$10^{-3}$至$0.1$的范围内变化。无论初始的灰尘与气体的比例，我们发现快速浓度的灰尘内的漩涡，达到灰尘与气体的比例的顺序统一内的漩涡。我们提出了一个分析模型，很好地描述了旋涡内的灰尘捕获过程，找到一致的结果，所有的灰尘与气体的比例。涡流不稳定性的发展必然导致涡流的破坏。涡消散后，在大多数情况下形成大尺度的尘埃环，围绕盘环，维持非常高的粉尘浓度，接近于一阶比。光环的寿命与模拟的持续时间一样长。它们还发展出流动的不稳定性，表现为不同尺度的漩涡，其中尘埃形成致密的高密度团块。如果没有粘性力的强烈耗散，这种团块将不稳定到引力坍缩。当漩涡特别长寿时，环不会形成，但漩涡内的尘埃团成为长寿的特征，并可能因引力不稳定而崩溃。环几乎包含了地球质量的固体物质，而在早期阶段，更大质量的尘埃确实会在漩涡中积累。我们认为，快速星子的形成将发生在尘埃团内的旋涡以及在后涡环。

英文摘要：

We study dust capture by vortices and its long-term consequences in global two-fluid inviscid disk simulations using a new polar grid code RoSSBi. We perform the longest integrations so far, several hundred disk orbits, at the highest resolution attainable in global simulations of disks with dust, namely 2048x4096 grid points. This allows to study the dust evolution well beyond vortex dissipation. We vary a wide range of parameters, most notably the dust-to-gas ratio in the initial setup varies in the range $10^{-3}$ to $0.1$. Irrespective of the initial dust-to-gas ratio we find rapid concentration of the dust inside vortices, reaching dust-to-gas ratios of order unity inside the vortex. We present an analytical model that describes very well the dust capture process inside vortices, finding consistent results for all dust-to-gas ratios. A vortex streaming instability develops which causes invariably vortex destruction. After vortex dissipation large-scale dust-rings encompassing a disk annulus form in most cases, which sustain very high dust concentration, approaching ratios of order unity. The rings are long lived lasting as long as the duration of the simulations. They also develop a streaming instability, which manifests itself in eddies at various scales within which the dust forms compact high density clumps. Such clumps would be unstable to gravitational collapse in absence of strong dissipation by viscous forces. When vortices are particularly long lived, rings do not form but dust clumps inside vortices become then long lived features and would likely undergo collapse by gravitational instability. Rings encompass almost an Earth mass of solid material, while even larger masses of dust do accumulate inside vortices in the earlier stage. We argue that rapid planetesimal formation would occur in the dust clumps inside the vortices as well as in the post-vortex ring.

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英文摘要：

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