Kinematics of the H2O Masers in W49N: Analysis of the Velocity Variance-Covariance Matrix
Kinematics of the H2O Masers in W49N: Analysis of the Velocity Variance-Covariance Matrix
复制标题
W49N 中 H2O 微波激射器的运动学：速度方差-协方差矩阵分析
DOI：
10.1086/308714
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
E. Bloemhof
中科院分区：
文献类型：
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作者：
E. Bloemhof
用Gwinn，Moran和Reid的多历元甚长基线干涉仪（VLBI）测量了W49N中H2O脉泽的自行。推导出的运动数量很大（105），微波激射点的源的空间覆盖范围很好，使W49 N成为基于速度方差协方差矩阵（VVCM）对角化的分析工具的自然候选者。VVCM分析中所用的速度频散（或内部相对速度）是由VLBI自行实验直接确定的量，它缺乏绝对相位参考。我适用于W49N的H2O脉泽的VVCM对角化程序，导出在一个客观的，模型无关的方式流出的运动轴。然后，我比较这些地方的轴与各种几何轴建议的形态的一个明显的“环”的H II地区，伴随着一个包含H2O脉泽，并与轴的大规模流出看到的分子发射。我还提出了运动学的证据，没有发现以前的建模明显的不对称性的准直机制，通道脉泽外流，并提出了一个解释的磁阻力。
The proper motions of the H2O masers in W49N have been measured with multiepoch very long baseline interferometry (VLBI) by Gwinn, Moran, & Reid. The number of motions derived is large (105), and the spatial coverage of the source by maser spots is excellent, making W49N a natural candidate for analytic tools based on diagonalization of the velocity variance-covariance matrix (VVCM). The velocity dispersions (or internal relative velocities) used in VVCM analysis are the quantities directly determined by VLBI proper motion experiments, which lack an absolute phase reference. I apply the VVCM diagonalization procedure to the H2O masers in W49N, deriving in an objective, model-independent way the kinematic axes of the outflow. I then compare these local axes with various geometrical axes suggested by the morphology of an apparent "ring" of H II regions that accompany the one containing H2O masers, and with the axis of the large-scale outflow seen in molecular emission. I also present kinematic evidence not revealed by previous modeling for pronounced asymmetry of the collimating mechanism that channels the maser outflow, and propose an explanation in terms of magnetic drag.