由RAVE估算恒星速度椭球的半径及其对质量模型的意义
Estimation of the Tilt of the Stellar Velocity Ellipsoid from RAVE and Implications for Mass Models
摘要：
我们提出了一个措施的倾斜速度椭球在1千秒差距以下的银河系平面使用样本的红丛巨星从RAVE DR 2释放。我们发现速度椭球以7.3 +/-1.8度的倾角向银道面倾斜。我们比较这个值计算的银河系的两个质量模型的倾角。我们发现，如果暗晕是扁圆的，我们的测量结果与星盘的短尺度长度（Rd ~ 2kpc）相一致，如果暗晕是扁长的，我们的测量结果与星盘的长尺度长度（Rd~3 kpc）相一致。一旦结合独立的限制平坦的晕，我们的测量表明，规模的长度大约是这两个极端值之间的一半，与一个接近球形晕的首选范围[2.5-2.7]千秒差距。然而，没有一种模式可以明确排除。随着RAVE巡天的继续，将有可能利用对速度椭球方向的精确测量，对银河系的质量分布提供强有力的约束。
英文摘要：
We present a measure of the inclination of the velocity ellipsoid at 1 kpc below the Galactic plane using a sample of red clump giants from the RAVE DR2 release. We find that the velocity ellipsoid is tilted towards the Galactic plane with an inclination of 7.3 +/-1.8 degree. We compare this value to computed inclinations for two mass models of the Milky Way. We find that our measurement is consistent with a short scale length of the stellar disc (Rd ~2 kpc) if the dark halo is oblate or with a long scale length (Rd~3 kpc) if the dark halo is prolate. Once combined with independent constraints on the flattening of the halo, our measurement suggests that the scale length is approximately halfway between these two extreme values, with a preferred range [2.5-2.7] kpc for a nearly spherical halo. Nevertheless, no model can be clearly ruled out. With the continuation of the RAVE survey, it will be possible to provide a strong constraint on the mass distribution of the Milky Way using refined measurements of the orientation of the velocity ellipsoid.
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