标题： 用贝叶斯推断检测球状星团潮汐延伸：I. 使用盖亚EDR3分析$ω$半人马座 显示英文标题

标题： Detecting Globular Cluster Tidal Extensions with Bayesian Inference: I. Analysis of $ω$ Centauri with Gaia EDR3

摘要： 星团（GCs）的外围区域由于其低表面亮度特性以及视线方向上银河系污染天体的主导而极难研究。我们通过在空间和自行空间中利用混合模型来解决这个问题，该模型分别对星团、晕外和污染恒星种群进行建模。我们通过应用Gaia EDR3的测光和天体测量数据到NGC 5139（$\omega$Cen）方向来展示我们方法的有效性，这是一个极具挑战性的目标，因其银河纬度（$b\approx 15^{\circ}$）和与周围场星的自行对比度较低。我们恢复了壮观的潮汐延伸部分，覆盖了在此处探索的$10^{\circ}$天空区域，这些在早期工作中已观察到，并量化了系统在距星团中心半径为$4^{\circ}$处的星数分布和椭率。我们表明，与属于$\omega$Cen一致的RR Lyr变星和蓝水平分支恒星出现在潮汐尾部，并计算出这些延伸部分包含系统总恒星质量至少$\approx 0.1$%。我们的高概率成员为未来对$\omega$Cen在前所未有的半径范围内的光谱研究提供了理想目标。 显示英文摘要

摘要： The peripheral regions of globular clusters (GCs) are extremely challenging to study due to their low surface brightness nature and the dominance of Milky Way contaminant populations along their sightlines. We have developed a probabilistic approach to this problem through utilising a mixture model in spatial and proper motion space which separately models the cluster, extra-tidal and contaminant stellar populations. We demonstrate the efficacy of our method through application to Gaia EDR3 photometry and astrometry in the direction of NGC 5139 ($\omega$ Cen), a highly challenging target on account of its Galactic latitude ($b\approx 15^{\circ}$) and low proper motion contrast with the surrounding field. We recover the spectacular tidal extensions, spanning the $10^{\circ}$ on the sky explored here, seen in earlier work and quantify the star count profile and ellipticity of the system out to a cluster-centric radius of $4^{\circ}$. We show that both RR Lyrae and blue horizontal branch stars consistent with belonging to $\omega$ Cen are found in the tidal tails, and calculate that these extensions contain at least $\approx 0.1$ per cent of the total stellar mass in the system. Our high probability members provide prime targets for future spectroscopic studies of $\omega$ Cen out to unprecedented radii.