A Large Local Rotational Speed for the Galaxy Found from Proper Motions: Implications for the Mass of the Milky Way
A Large Local Rotational Speed for the Galaxy Found from Proper Motions: Implications for the Mass of the Milky Way
复制标题
DOI：
10.1086/312292
复制
发表时间：
1999-08
期刊：
影响因子：
--
通讯作者：
R. M'endez;I. Platais;T. Girard;V. Kozhurina-Platais;W. V. van Altena
中科院分区：
文献类型：
--
作者：
R. M'endez;I. Platais;T. Girard;V. Kozhurina-Platais;W. V. van Altena
从银河系结构和运动学模型的预测进行了比较，约30,000个随机选择的恒星的绝对自行9 < BJ ≤ 19从南方自行（SPM）计划向南银河系极。SPM自行的绝对性质使我们不仅可以测量太阳相对于本地磁盘的相对运动，而且最重要的是，本地磁盘相对于星系的整体旋转状态。SPM数据最适合的模型有一个5公里s-1的太阳特有的运动在V-分量（指向银河系旋转的方向），一个大LSR速度为270公里s-1，和一个磁盘速度椭球指向银河系中心。然而，我们强调，这些结果关键在于轴对称和平衡动力学的假设。U分量中的绝对自行表明太阳的特有运动为11.0 ± 1.5 km s-1，不需要局部膨胀或收缩项。大LSR的速度的影响进行了讨论，在银河系的引力质量推断，从最近和准确的测定自行的LMC。我们发现，我们导出的LSR值与根据星云运动推断的银河系质量[（3-4）× 1012 M ~~50 kpc]以及基于M31和银河系以及Leo I和银河系的双星运动的时间参数（≥1.2 × 1012 M ~200 kpc）是一致的。
Predictions from a Galactic structure and kinematic model are compared with the absolute proper motions of about 30,000 randomly selected stars with 9 < BJ ≤ 19 derived from the Southern Proper-Motion (SPM) program toward the south Galactic pole. The absolute nature of the SPM proper motions allows us to measure not only the relative motion of the Sun with respect to the local disk but also, and most importantly, the overall state of rotation of the local disk with respect to galaxies. The SPM data are best fitted by models having a solar peculiar motion of 5 km s-1 in the V-component (pointing in the direction of Galactic rotation), a large LSR speed of 270 km s-1, and a disk velocity ellipsoid that points toward the Galactic center. We stress, however, that these results rest crucially on the assumptions of both axisymmetry and equilibrium dynamics. The absolute proper motions in the U-component indicate a solar peculiar motion of 11.0 ± 1.5 km s-1, with no need for a local expansion or contraction term. The implications of the large LSR speed are discussed in terms of the gravitational mass of the Galaxy inferred from the most recent and accurate determination for the proper motion of the LMC. We find that our derived value for the LSR is consistent both with the mass of the Galaxy inferred from the motion of the Clouds [(3-4) × 1012 M☉ to ~50 kpc] and with the timing argument, based on the binary motion of M31 and the Milky Way and on that of Leo I and the Milky Way (≥1.2 × 1012 M☉ to ~200 kpc).