不是随风而逝：行星的出现与恒星的银河系速度无关
Not Gone with the Wind: Planet Occurrence is Independent of Stellar Galactocentric Velocity
摘要：
我们证明，行星的发生并不依赖于恒星的银河系中心的速度在太阳附近。使用盖亚DR 2天体测量和径向速度数据，我们计算了197，090开普勒场恒星的3D银河系速度，其中1647颗被确认为行星宿主。当我们将行星宿主的银河系速度与整个场星样本的银河系速度进行比较时，我们观察到一个统计上显著的（KS p值= $10^{-70}$）区别，行星宿主明显比场星慢$\sim$ 40 km/s。我们探讨了这种差异的一些潜在的解释，并得出结论，这不是行星金属丰度关系或样品的薄/厚盘成员的区别的结果，而是开普勒的选择函数的人工制品。非开普勒宿主恒星与已确认的行星宿主有几乎相同的距离、温度、表面重力和开普勒星等，也有几乎相同的速度分布。使用这些相同的非主机样本之一，我们认为，一个恒星的速度$v_{\mathrm{tot}}$托管行星的概率可以描述的指数函数成正比于$e^{(-v_{\mathrm{tot}}/v_0)}$。使用马尔可夫链蒙特卡罗采样器，我们确定$v_0 > $ 976 km/s到99%的置信度，这意味着在太阳附近的行星是一样有可能形成围绕快恒星，因为它们是围绕慢恒星。我们的工作突出了选择偏差可以在没有物理基础的情况下产生强相关性的微妙方式。
英文摘要：
We demonstrate that planet occurrence does not depend on stellar galactocentric velocity in the Solar neighborhood. Using Gaia DR2 astrometry and radial velocity data, we calculate 3D galactocentric velocities for 197,090 Kepler field stars, 1647 of which are confirmed planet hosts. When we compare the galactocentric velocities of planet hosts to those of the entire field star sample, we observe a statistically significant (KS p-value = $10^{-70}$) distinction, with planet hosts being apparently slower than field stars by $\sim$40 km/s. We explore some potential explanations for this difference and conclude that it is not a consequence of the planet-metallicity relation or distinctions in the samples' thin/thick disk membership, but rather an artefact of Kepler's selection function. Non Kepler-host stars that have nearly identical distances, temperatures, surface gravities, and Kepler magnitudes to the confirmed planet hosts also have nearly identical velocity distributions. Using one of these identical non-host samples, we consider that the probability of a star with velocity $v_{\mathrm{tot}}$ hosting a planet can be described by an exponential function proportional to $e^{(-v_{\mathrm{tot}}/v_0)}$. Using a Markov Chain Monte Carlo sampler, we determine that $v_0 > $976 km/s to 99% confidence, which implies that planets in the Solar neighborhood are just as likely to form around fast stars as they are around slow stars. Our work highlights the subtle ways in which selection biases can create strong correlations without physical underpinnings.
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