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Structure and Internal Kinematics of Nine Inner Milky Way Globular Clusters
The Astronomical Journal ( IF 5.1 ) Pub Date : 2020-12-22 , DOI: 10.3847/1538-3881/abd036
Roger E. Cohen 1 , Andrea Bellini 1 , Mattia Libralato 1 , Matteo Correnti 1 , Thomas M. Brown 1 , Jason S. Kalirai 2
Affiliation  

This study constitutes part of a larger effort aimed at better characterizing the Galactic globular clusters (GGCs) located towards the inner Milky Way bulge and disk. Here, we focus on internal kinematics of nine GGCs, obtained from space-based imaging over time baselines of $>$9 years. We exploit multiple avenues to assess the dynamical state of the target GGCs, constructing radial profiles of projected stellar density, proper motion dispersion, and anisotropy. We posit that two-thirds (6/9) of our target GGCs are in an advanced dynamical state, and are close to (or have recently undergone) core collapse, supported by at least two lines of evidence: First, we find relatively steep proper motion dispersion profiles, in accord with literature values for core-collapsed GGCs. Second, we find that our sample is, in the mean, isotropic even out to their half-light radii, although one of our target clusters (NGC 6380) is tangentially anisotropic at $>$1$\sigma$ beyond its half-light radius, in accord with theoretical predictions for clusters evolving in strong tidal fields. Our proper motion dispersion and anisotropy profiles are made publicly available.

中文翻译:

九个内部银河系球状星团的结构和内部运动学

这项研究是一项更大努力的一部分,旨在更好地表征位于银河系内部凸起和圆盘的星系球状星团 (GGC)。在这里,我们专注于九个 GGC 的内部运动学,这些 GGC 是从超过 9 美元的时间基线的天基成像中获得的。我们利用多种途径来评估目标 GGC 的动力学状态,构建投影恒星密度、自行色散和各向异性的径向剖面。我们假设三分之二 (6/9) 的目标 GGC 处于高级动态状态,并且接近(或最近经历过)核心坍塌,至少有两条证据线支持:首先,我们发现相对陡峭自身运动色散曲线,与核心塌陷 GGC 的文献值一致。其次,我们发现我们的样本平均而言,尽管我们的目标星团之一 (NGC 6380) 在超过其半光半径的 $>$1$\sigma$ 处切向各向异性,但各向同性甚至达到其半光半径,这与在强潮汐场中演化的星团的理论预测一致. 我们的自身运动色散和各向异性分布是公开的。
更新日期:2020-12-22
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