确定潮汐流划定的轨道
Locating the orbits delineated by tidal streams
摘要：
我们描述了一种技术，发现通过银河系的轨道是一致的潮汐流的测量，考虑到潮汐流的程度不精确地描绘轨道。我们表明，如果沿着定义明确的流测量准确的视线速度，该技术可以恢复银河系的底层轨道，并高精度地预测沿着流的距离和自行。随着流的位置和速度的误差条的增长，该技术能够找到越来越多的与数据一致的轨道，预测距离和自行的不确定性增加。在天空中，沿一条长约40度、宽小于0.3度的流的径向速度数据精确到约1 km/s，沿流的距离和切向速度的精度分别为4%和5 km/s。该技术可用于诊断银河势：如果圆速度曲线实际上是平坦的，则很容易排除开普勒势和与r成比例的Phi（r）。如果有正确的暗晕径向密度分布，那么暗晕的质量可以精确到5%。
英文摘要：
We describe a technique that finds orbits through the Galaxy that are consistent with measurements of a tidal stream, taking into account the extent that tidal streams do not precisely delineate orbits. We show that if accurate line-of-sight velocities are measured along a well defined stream, the technique recovers the underlying orbit through the Galaxy and predicts the distances and proper motions along the stream to high precision. As the error bars on the location and velocities of the stream grow, the technique is able to find more and more orbits that are consistent with the data and the uncertainties in the predicted distances and proper motions increase. With radial-velocity data along a stream ~40deg long and <0.3deg wide on the sky accurate to ~1 km/s the precisions of the distances and tangential velocities along the stream are 4 percent and 5 km/s, respectively. The technique can be used to diagnose the Galactic potential: if circular-speed curve is actually flat, both a Keplerian potential and Phi(r) proportional to r are readily excluded. Given the correct radial density profile for the dark halo, the halo's mass can be determined to a precision of 5 percent.
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