THE DISTANCE TO A STAR-FORMING REGION IN THE OUTER ARM OF THE GALAXY
THE DISTANCE TO A STAR-FORMING REGION IN THE OUTER ARM OF THE GALAXY
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DOI：
10.1088/0004-637x/696/2/1981
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发表时间：
2009-01
期刊：
影响因子：
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通讯作者：
K. Hachisuka;A. Brunthaler;K. Menten;M. Reid;Y. Hagiwara;N. Mochizuki
中科院分区：
文献类型：
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作者：
K. Hachisuka;A. Brunthaler;K. Menten;M. Reid;Y. Hagiwara;N. Mochizuki
我们使用 WB89−437 的超长基线军（位于银河系外旋臂的 H2O 脉泽源）进行了天体测量。我们测量到的年视差为 0.167 ± 0.006 mas，对应于日心距离为 6.0 ± 0.2 kpc 或银河心距为 13.4 ± 0.2 kpc。该日心距离值远小于 8.6 kpc 的运动距离。这证实了存在朝向 l = 135° 的微弱外臂。我们还测量了该物体的整个空间运动，并发现了一个朝向银河系中心约 20 km s−1 的大奇特运动。这种特殊的运动解释了运动距离估计中的巨大误差。我们还发现 WB89−437 具有与 LSR 相同的旋转速度，为平坦旋转曲线以及外星系中暗物质的存在提供了更多证据。
We performed astrometric observations with the Very Long Baseline Army of WB89−437, an H2O maser source in the Outer spiral arm of the Galaxy. We measure an annual parallax of 0.167 ± 0.006 mas, corresponding to a heliocentric distance of 6.0 ± 0.2 kpc or a Galactocentric distance of 13.4 ± 0.2 kpc. This value for the heliocentric distance is considerably smaller than the kinematic distance of 8.6 kpc. This confirms the presence of a faint Outer arm toward l = 135°. We also measured the full space motion of the object and find a large peculiar motion of ∼20 km s−1 toward the Galactic center. This peculiar motion explains the large error in the kinematic distance estimate. We also find that WB89−437 has the same rotation speed as the LSR, providing more evidence for a flat rotation curve and thus the presence of dark matter in the outer Galaxy.