论文标题
分析PDS 70的外磁盘中的臂状结构。螺旋密度波还是涡流？
Analysis of the arm-like structure in the outer disk of PDS 70. Spiral density wave or vortex?
论文作者
论文摘要
观察行星和磁盘之间的动态相互作用是理解它们的形成和进化的关键。最近在PDS 70的Protoplanetary磁盘中发现了两个原型，以及沿恒星西北的臂状结构。我们的目的是限制这种类似臂状结构的形态和起源，并评估它是否可以追踪由Planet PDS 70C和磁盘之间的动态相互作用引起的螺旋密度波。我们分析了用VLT/Sphere获取的极化和角度差异成像（PDI和ADI）数据，涵盖了六年的观察结果。使用IRDAP极化数据减少管道减少了PDI数据集，而ADI数据集则使用芥末处理（一种新型的逆问题算法来处理，以应对几何偏见，破坏了先前用于该磁盘分析的图像。我们确认所有PDI和ADI数据集中的臂状结构的存在。我们没有观察到有关磁盘次要轴的东南对称臂，这似乎不利于先前的假设，即手臂是双环结构的足迹。如果结构在PDS 70C运动后跟踪螺旋密度波，则我们希望$ 11 \ Overset {\ Circ} {。} 28^{+2 \ 2 \ Overset {\ Crip} {。} 20} _ { - 0 \ 0 \ overset {\ circ} {\ circ} {。但是，我们不能衡量结构的任何重大运动。如果臂状结构是行星驱动的螺旋臂，则观察到的旋转不足将表明，刚体旋转的假设可能不适合行星引起的螺旋。我们建议，由于投影效应，臂状结构可能宁愿追踪在散射光中作为单臂螺旋出现的涡流。涡流假说既说明了观察到的旋转缺乏，也说明了用ALMA检测到的附近亚MM连续性不对称。
Observing dynamical interactions between planets and disks is key to understanding their formation and evolution. Two protoplanets have recently been discovered within PDS 70's protoplanetary disk, along with an arm-like structure towards the north-west of the star. Our aim is to constrain the morphology and origin of this arm-like structure, and to assess whether it could trace a spiral density wave caused by the dynamical interaction between the planet PDS 70c and the disk. We analyze polarized and angular differential imaging (PDI and ADI) data taken with VLT/SPHERE, spanning six years of observations. PDI data sets are reduced using the IRDAP polarimetric data reduction pipeline, while ADI data sets are processed using MUSTARD, a novel inverse problem algorithm to tackle the geometrical biases spoiling the images previously used for the analysis of this disk. We confirm the presence of the arm-like structure in all PDI and ADI datasets. We do not observe a south-east symmetric arm with respect to the disk minor axis, which seems to disfavor the previous hypothesis that the arm is the footprint of a double-ring structure. If the structure traces a spiral density wave following the motion of PDS 70c, we would expect $11\overset{\circ}{.}28^{+2\overset{\circ}{.}20}_{-0\overset{\circ}{.}86}$ rotation for the spiral in six years. However, we do not measure any significant movement of the structure. If the arm-like structure is a planet-driven spiral arm, the observed lack of rotation would suggest that the assumption of rigid-body rotation may be inappropriate for spirals induced by planets. We suggest that the arm-like structure may rather trace a vortex appearing as a one-armed spiral in scattered light due to projection effects. The vortex hypothesis accounts for both the lack of observed rotation and the presence of a nearby sub-mm continuum asymmetry detected with ALMA.
