发表机构
XinJiang Astronomical Observatory, Chinese Academy of Sciences; School of Astronomy and Space Science, University of Chinese Academy of Sciences; University of Massachusetts Amherst; Astronomical Institute of the Czech Academy of Sciences; Center for Astrophysics | Harvard & Smithsonian; Department of Astrophysics, University of Vienna（中国科学院新疆天文台; 中国科学院大学天文与空间科学学院; 马萨诸塞大学阿默斯特分校; 捷克科学院天文研究所; 哈佛史密森尼天体物理中心; 维也纳大学天体物理系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用两点相关函数分析银河系疏散星团的聚集特性，发现年轻星团保留恒星形成的层级结构，随年龄增长聚集在约100 Myr内消退，并建立了投影与三维分形维数的经验映射。
AI 中文摘要
银河系疏散星团既记录了层级式恒星形成过程，也记录了银河系盘随后的动力学演化。我们利用两点相关函数来表征太阳邻域内疏散星团的空间与运动学聚集特性，考虑其三维（3D）分布及其在银道面上的投影，以及按年龄、质量与巡天体积划分的子样本。我们通过分形维数和特征相关尺度来量化聚集程度。我们发现，最年轻的星团其分形维数与星际介质中测得的数值相当，表明它们保留了其诞生分子云的部分层级结构。随后，聚集强度随年龄系统性减弱，并在约100 Myr的特征时间尺度上变得微弱。这种演化具有尺度依赖性：在数十秒差距尺度上的过剩相关比在数百秒差距尺度上较微弱的相关消退得更快。相比之下，我们发现聚集特性对星团质量和体积的依赖性较弱。利用同一星团样本，我们推导出投影分形维数与三维分形维数之间的经验映射，为将银河系与仅能获得投影测量的外部星系研究进行比较提供了观测校准。疏散星团群体分别表现出约370 pc和11 km/s的特征空间与运动学聚集尺度。这些结果支持这样一种图景：年轻的疏散星团从恒星形成中继承了空间层级结构，并通过后续演化逐渐失去其空间相关性。
英文摘要
Galactic open clusters provide a record of both hierarchical star formation and the subsequent dynamical evolution of the Milky Way disk. We use the two-point correlation function to characterize the spatial and kinematic clustering of open clusters in the solar neighborhood, considering their three-dimensional (3D) distributions and their projections onto the Galactic plane, as well as subsamples divided by age, mass, and survey volume. We quantify the clustering through fractal dimensions and characteristic correlation scales. We find that the youngest clusters have fractal dimensions comparable to those measured in the interstellar medium, suggesting that they retain part of the hierarchical structure of their natal molecular clouds. The clustering strength then decreases systematically with age and becomes weak on a characteristic timescale of order 100 Myr. This evolution is scale dependent: the excess correlation at tens of parsecs fades more rapidly than the weaker correlation at hundreds of parsecs. By contrast, we find only a weak dependence of the clustering properties on cluster mass and volume. Using the same cluster sample, we derive an empirical mapping between projected and 3D fractal dimensions, providing an observational calibration for comparing the Milky Way with studies of external galaxies, where only projected measurements are available. The open-cluster population exhibits characteristic spatial and kinematic clustering scales of approximately 370 pc and 11 km/s, respectively. These results support a picture in which young open clusters inherit a spatial hierarchy from star formation and progressively lose their spatial correlations through subsequent evolution.
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