球状星团流作为银河系的高精度尺度-海报儿童帕洛马5
Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5
摘要：
以银河系球状星团Palomar 5（PAL 5）的潮汐流为例，我们演示了如何有效地降低流的观测数据的维数，并在贝叶斯框架中建模。我们的方法结合检测流overdensities的差分高斯过程与快速条纹线模型，从这些模型建立的连续似然函数，并与MCMC推理。通过生成$\approx10^7$模型流，我们表明，的几何形状的105碎片产生强大的约束太阳的位置和运动，银河系和105本身。允许所有10个模型参数在大范围内变化，而无需额外的先验信息。仅用SDSS数据和文献中的一些径向速度，我们发现太阳到银河系中心的距离为$8.30\pm0.25$ kpc，横向速度为$253\pm16$ km/s。这两个估计值都与这些量的独立测量值非常一致。假设一个标准的盘和隆起模型，我们确定银河系质量范围内的银河系5的远距星系半径为19 kpc的$(2.1\pm0.4)\times10^{11}$ M $_\odot$。此外，我们发现潜在的黑暗晕与平坦的$q_z = 0.95^{+0.16}_{-0.12}$基本上是球形的径向范围内，是有效地探测到的。我们还独立于其他方法确定了E15的质量，距离和自行，这使我们能够进行重要的交叉检查。我们的结论是，更多的观测数据，并通过使用额外的先验信息，这种方法的精度可以显着提高。
英文摘要：
Using the example of the tidal stream of the Milky Way globular cluster Palomar 5 (Pal 5), we demonstrate how observational data on streams can be efficiently reduced in dimensionality and modeled in a Bayesian framework. Our approach combines detection of stream overdensities by a Difference-of-Gaussians process with fast streakline models, a continuous likelihood function built from these models, and inference with MCMC. By generating $\approx10^7$ model streams, we show that the geometry of the Pal 5 debris yields powerful constraints on the solar position and motion, the Milky Way and Pal 5 itself. All 10 model parameters were allowed to vary over large ranges without additional prior information. Using only SDSS data and a few radial velocities from the literature, we find that the distance of the Sun from the Galactic Center is $8.30\pm0.25$ kpc, and the transverse velocity is $253\pm16$ km/s. Both estimates are in excellent agreement with independent measurements of these quantities. Assuming a standard disk and bulge model, we determine the Galactic mass within Pal 5's apogalactic radius of 19 kpc to be $(2.1\pm0.4)\times10^{11}$ M$_\odot$. Moreover, we find the potential of the dark halo with a flattening of $q_z = 0.95^{+0.16}_{-0.12}$ to be essentially spherical within the radial range that is effectively probed by Pal 5. We also determine Pal 5's mass, distance and proper motion independently from other methods, which enables us to perform vital cross-checks. We conclude that with more observational data and by using additional prior information, the precision of this method can be significantly increased.
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