第三纪麦哲伦云自行II：三维大麦云云自转场
Third-Epoch Magellanic Cloud Proper Motions II: The Large Magellanic Cloud Rotation Field in Three Dimensions
摘要：
我们提出了第一个详细的评估的大规模旋转的任何星系的基础上完整的三维速度测量。我们这样做的LMC结合我们的HST平均自行（PM）测量的恒星在22个领域，与现有的视线（LOS）速度测量6790个单独的恒星。我们解释这些数据与一个模型的圆旋转在一个扁平的磁盘。PM和LOS数据描绘了LMC旋转的一致画面，它们的组合产生了一些新的见解。PM数据意味着一个恒星的动力学中心，与HI动力学中心相一致，和旋转曲线振幅与从LOS速度研究推断一致。隐含的圆盘视角与文献中发现的值的范围一致，但继续表明恒星星族和/或半径的变化。由于不对称漂移，年轻的（RSG）恒星比年老的（RGB/AGB）恒星旋转得更快。在中心区域之外，圆速度在Vcirc = 91.7 +/- 18.8 km/s处近似平坦。这与重子的塔利-费雪关系相一致，并意味着封闭质量M（8.7 kpc）=（1.7 +/- 0.7）x 10^10太阳质量。维里质量较大，取决于暗晕的完整范围。潮汐半径为22.3 +/- 5.2千秒差距（24.0 +/- 5.6度）。PM和LOS数据的组合产生LMC的运动学距离估计，但这些还没有与其他方法竞争。
英文摘要：
We present the first detailed assessment of the large-scale rotation of any galaxy based on full three-dimensional velocity measurements. We do this for the LMC by combining our HST average proper motion (PM) measurements for stars in 22 fields, with existing line-of-sight (LOS) velocity measurements for 6790 individual stars. We interpret these data with a model of circular rotation in a flat disk. The PM and LOS data paint a consistent picture of the LMC rotation and their combination yields several new insights. The PM data imply a stellar dynamical center that coincides with the HI dynamical center, and a rotation curve amplitude consistent with that inferred from LOS velocity studies. The implied disk viewing angles agree with the range of values found in the literature, but continue to indicate variations with stellar population and/or radius. Young (RSG) stars rotate faster than old (RGB/AGB) stars due to asymmetric drift. Outside the central region, the circular velocity is approximately flat at Vcirc = 91.7 +/- 18.8 km/s. This is consistent with the baryonic Tully-Fisher relation, and implies an enclosed mass M(8.7 kpc) = (1.7 +/- 0.7) x 10^10 solar masses. The virial mass is larger and depends on the full extent of the dark halo. The tidal radius is 22.3 +/- 5.2 kpc (24.0 +/- 5.6 degrees). Combination of the PM and LOS data yields kinematic distance estimates for the LMC, but these are not yet competitive with other methods.
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