MWC 758原行星盘中尘埃团块自行运动的ALMA观测
ALMA Observations of Proper Motions of the Dust Clumps in the Protoplanetary Disk MWC 758
AI总结：
本研究利用ALMA在2017和2021年的观测数据，分析了MWC 758原行星盘中两个尘埃团块的自行运动，发现其呈现非开普勒运动，推测这是尘埃团块与盘内旋臂相互作用导致密度分布变化所致。
AI中文摘要：
为了研究MWC 758周围原行星盘内尘埃捕获涡旋中的尘埃动力学，我们分析了2017年和2021年利用阿塔卡马大型毫米/亚毫米波阵列（ALMA）获取的MWC 758盘的1.3 mm连续谱图像。我们在天球平面上分别探测到盘内位于半径0\farcs32和0\farcs54处的两个尘埃团块存在22 mas和24 mas的自行运动。假设尘埃团块位于盘的中面，内、外尘埃团块沿方位角方向的观测自行运动速度分别为亚开普勒速度和超开普勒速度，且两者的角速度均对应于半径$0\farcs46\pm0\farcs04$处的开普勒角速度。这种对开普勒运动的偏离在由Rossby波不稳定性形成的涡旋传统理论中是无法预期的。观测到的尘埃团块非开普勒自行运动不太可能是由盘的扭曲和偏心率引起的，也不与任何预测的行星相关。这两个尘埃团块可能在空间上与红外旋臂重合。此外，我们探测到了尘埃团块强度分布在四年跨度内的变化。因此，我们认为观测到的自行运动可能是由于尘埃团块与盘内旋臂相互作用导致其密度分布发生变化所致。
英文摘要：
To study the dust dynamics in the dust trapping vortices in the protoplanetary disk around MWC~758, we analyzed the 1.3 mm continuum images of the MWC~758 disk obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) in 2017 and 2021. We detect proper motions of 22 mas and 24 mas in the two dust clumps at radii of 0\farcs32 and 0\farcs54 in the disk on the plane of the sky, respectively. On the assumption that the dust clumps are located in the disk midplane, the velocities of the observed proper motions along the azimuthal direction of the inner and outer dust clumps are sub- and super-Keplerian, respectively, and both have angular velocities corresponding to the Keplerian angular velocity at a radius of $0\farcs46\pm0\farcs04$. This deviation from the Keplerian motion is not expected in the conventional theory of vortices formed by the Rossby wave instability. The observed non-Keplerian proper motions of the dust clumps are unlikely due to the disk warp and eccentricity, nor be associated with any predicted planets. The two dust clumps are likely spatially coincident with the infrared spirals. In addition, we detect the changes in the intensity profiles of the dust clumps over the four-year span. Therefore, we suggest that the observed proper motions are possibly due to changes in the density distributions in the dust clumps caused by their interaction with the spirals in the disk.
