Velocity Trends in the Debris of Sagittarius and the Shape of the Dark Matter Halo of Our Galaxy
Velocity Trends in the Debris of Sagittarius and the Shape of the Dark Matter Halo of Our Galaxy
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DOI：
10.1086/423340
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发表时间：
2004-06
期刊：
影响因子：
--
通讯作者：
A. Helmi
中科院分区：
文献类型：
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作者：
A. Helmi
最近，从2微米全天巡天目录中选取了大量M巨星样本，测量了它们的径向速度，这些样本被选作Sgr矮星的先导流和尾流的一部分。在这里，我们提出了一个比较他们的运动学模型的Sgr矮碎片轨道银河系的潜力，与晕组件的不同程度的扁平化和伸长。这种比较表明，迄今为止绘制的尾流部分在动态上很年轻，因此不会对银河系暗物质晕的形状提供非常严格的限制。然而，领先的流，包含稍微老一些的碎片，它的运动学提供了第一次直接的证据，我们的银河系的暗物质晕有一个扁长的形状，在Sgr轨道内的平均密度轴比接近5/3。
Recently, radial velocities have been measured for a large sample of M giants from the Two Micron All Sky Survey catalog, selected to be part of the Sgr dwarf leading and trailing streams. Here we present a comparison of their kinematics to models of the Sgr dwarf debris orbiting Galactic potentials, with halo components of varying degrees of flattening and elongation. This comparison shows that the portion of the trailing stream mapped so far is dynamically young and hence does not provide very stringent constraints on the shape of the Galactic dark matter halo. The leading stream, however, contains slightly older debris, and its kinematics provide for the first time direct evidence that the dark matter halo of our Galaxy has a prolate shape with an average density axis ratio within the orbit of Sgr close to 5/3.