A Family Picture: Tracing the Dynamical Path of the Structural Properties of Multiple Populations in Globular Clusters
A Family Picture: Tracing the Dynamical Path of the Structural Properties of Multiple Populations in Globular Clusters
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DOI：
10.3847/2041-8213/ab45f7
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发表时间：
2019-10
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影响因子：
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通讯作者：
E. Dalessandro;M. Cadelano;E. Vesperini;S. Martocchia;F. Ferraro;B. Lanzoni;N. Bastian;J. Hong;N. Sanna
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文献类型：
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作者：
E. Dalessandro;M. Cadelano;E. Vesperini;S. Martocchia;F. Ferraro;B. Lanzoni;N. Bastian;J. Hong;N. Sanna
我们研究了跨越广泛动力学年龄的 20 个球状星团 (GC) 样本中多个恒星族 (MP) 的空间分布。第一族 (FP) 和第二族 (SP) 恒星之间的差异通过参数 A+ 来测量，参数 A+ 定义为它们的累积径向分布之间包围的面积。我们提供了第一个纯粹的观察证据，证明 MP 从初始条件到完整的 FP-SP 空间混合所遵循的动力学路径。动态演化程度较低的星团中，SP 星比 FP 更集中，而在动态演化程度较高的系统中，FP 星和 SP 星之间的空间差异会减小并最终消失。通过与一组数值模拟的适当比较，我们表明这些观测结果与最初更集中的 SP 子系统形成的簇的长期动态演化所预期的演化顺序是一致的。这一结果得到了 A+ 与 GC 动力学演化阶段之间趋势的证据的进一步支持，该阶段是通过星团当前质量与初始质量之间的比率推断出来的。
We studied the spatial distributions of multiple stellar populations (MPs) in a sample of 20 globular clusters (GCs) spanning a broad range of dynamical ages. The differences between first-population (FP) and second-population (SP) stars were measured by means of the parameter A+, defined as the area enclosed between their cumulative radial distributions. We provide the first purely observational evidence of the dynamical path followed by MPs from initial conditions toward a complete FP–SP spatial mixing. Less dynamically evolved clusters have SP stars more centrally concentrated than FPs, while in more dynamically evolved systems the spatial differences between FP and SP stars decrease and eventually disappear. By means of an appropriate comparison with a set of numerical simulations, we show that these observational results are consistent with the evolutionary sequence expected by the long-term dynamical evolution of clusters forming with an initially more centrally concentrated SP subsystem. This result is further supported by the evidence of a trend between A+ and the stage of GC dynamical evolution inferred by the ratio between the present-day and the initial mass of the cluster.