WEAK TURBULENCE IN THE HD 163296 PROTOPLANETARY DISK REVEALED BY ALMA CO OBSERVATIONS
WEAK TURBULENCE IN THE HD 163296 PROTOPLANETARY DISK REVEALED BY ALMA CO OBSERVATIONS
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DOI：
10.1088/0004-637x/813/2/99
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发表时间：
2015-10
期刊：
影响因子：
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通讯作者：
K. Flaherty;A. Hughes;K. Rosenfeld;S. Andrews;E. Chiang;Jacob B. Simon;Jacob B. Simon;Skylar G. Kerzner;D. Wilner
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文献类型：
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作者：
K. Flaherty;A. Hughes;K. Rosenfeld;S. Andrews;E. Chiang;Jacob B. Simon;Jacob B. Simon;Skylar G. Kerzner;D. Wilner
湍流可以传递原行星盘中的角动量，影响行星的生长和演化。利用（亚）毫米干涉观测提供的空间和光谱分辨的分子发射线测量，可以直接测量圆盘气体中可归因于这种湍流的非热运动。我们报告了对HD 163296（一颗邻近的年轻a星）周围盘内湍流的新约束，这是由阿塔卡马大型毫米/亚毫米阵列科学验证观测到的四个CO发射线(CO(3-2)， CO（2-1), 13CO（2-1）和C18O（2-1）过渡）确定的。这些线的不同光学深度允许在一系列物理条件（温度和密度）和深度进入磁盘内部的非热线宽度探针。我们对外盘上层的非热运动给出了严格的限制，使得湍流对线宽的任何贡献都小于局部声速的3%。这些极限大约比由磁旋不稳定性驱动的全面磁流体动力学湍流的理论预测低一个数量级，潜在地表明这种机制在外层（R > 30 AU）盘的效率比以前认为的要低。
Turbulence can transport angular momentum in protoplanetary disks and influence the growth and evolution of planets. With spatially and spectrally resolved molecular emission line measurements provided by (sub)millimeter interferometric observations, it is possible to directly measure non-thermal motions in the disk gas that can be attributed to this turbulence. We report a new constraint on the turbulence in the disk around HD 163296, a nearby young A star, determined from Atacama Large Millimeter/submillimeter Array Science Verification observations of four CO emission lines (the CO(3-2), CO(2-1), 13CO(2-1), and C18O(2-1) transitions). The different optical depths for these lines permit probes of non-thermal line-widths at a range of physical conditions (temperature and density) and depths into the disk interior. We derive stringent limits on the non-thermal motions in the upper layers of the outer disk such that any contribution to the line-widths from turbulence is <3% of the local sound speed. These limits are approximately an order of magnitude lower than theoretical predictions for full-blown magnetohydrodynamic turbulence driven by the magnetorotational instability, potentially suggesting that this mechanism is less efficient in the outer (R ≳ 30 AU) disk than has been previously considered.