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The spatial structure and dynamical state of the open cluster NGC 2112
Publications of the Astronomical Society of Japan ( IF 2.2 ) Pub Date : 2021-04-10 , DOI: 10.1093/pasj/psab027
Xinhua Gao 1 , ShouKun Xu 1 , Lei Xue 1
Affiliation  

This paper investigates the spatial structure and dynamical state of the old open cluster NGC 2112 based on likely cluster members from Gaia Early Data Release 3. Using the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm, we find 1193 likely cluster members down to G ∼ 21 mag within a radius of 1.°5 from the cluster center. These likely cluster members can be divided into 865 core members and 328 border members by DBSCAN. We find that the core members are, on average, significantly brighter and more centrally concentrated than the border members. This suggests the existence of clear mass segregation within the cluster. We find that the outer regions of the cluster exhibit a slightly elongated shape, which may be caused by external tidal perturbations. We estimate a distance of D = 1108 ± 3 pc for the cluster based on bright core members. We find that NGC 2112 has a cluster radius of Rcl ∼ 40′ (∼12.9 pc) and a core radius of $R_{\rm c} \sim {4{^{\prime }_{.}}8} \pm {0{^{\prime }_{.}}2}$ (∼1.5 pc). This indicates that NGC 2112 has a central concentration parameter of C = log (Rcl/Rc) ∼ 0.92, which is significantly larger than previously thought. In addition, we estimate a total mass of Mcl = 858 ± 12 M⊙ and an initial mass of Mini = (2.2 ± 0.5) × 104 M⊙ for the cluster. This implies that NGC 2112 may have lost more than $90\%$ of its initial mass. Based on the obtained distance and kinematical data, we also calculate the Galactic orbit of the cluster.

中文翻译:

疏散星团NGC 2112的空间结构和动力学状态

本文基于 Gaia Early Data Release 3 中可能的星团成员研究旧疏散星团 NGC 2112 的空间结构和动态状态。使用基于密度的噪声应用空间聚类 (DBSCAN) 算法,我们发现了 1193 个可能的星团成员在距星团中心 1.°5 的半径范围内下降到 G ∼ 21 mag。DBSCAN将这些可能的集群成员划分为865个核心成员和328个边界成员。我们发现,平均而言,核心成员比边界成员更明亮、更集中。这表明集群内存在明显的质量隔离。我们发现星团的外部​​区域呈现出略微拉长的形状,这可能是由外部潮汐扰动引起的。我们根据明亮的核心成员估计集群的距离为 D = 1108 ± 3 pc。我们发现 NGC 2112 的星团半径为 Rcl ∼ 40′ (∼12.9 pc),核心半径为 $R_{\rm c} \sim {4{^{\prime }_{.}}8} \pm {0{^{\prime }_{.}}2}$(∼1.5 个)。这表明 NGC 2112 的中心浓度参数为 C = log (Rcl/Rc) ∼ 0.92,比之前认为的要大得多。此外,我们估计星团的总质量 Mcl = 858 ± 12 M⊙ 和 Mini = (2.2 ± 0.5) × 104 M⊙ 的初始质量。这意味着 NGC 2112 可能已经损失了超过 90\%$ 的初始质量。根据获得的距离和运动学数据,我们还计算了星团的银河轨道。}}8} \pm {0{^{\prime }_{.}}2}$(∼1.5 个)。这表明 NGC 2112 的中心浓度参数为 C = log (Rcl/Rc) ∼ 0.92,比之前认为的要大得多。此外,我们估计星团的总质量 Mcl = 858 ± 12 M⊙ 和 Mini = (2.2 ± 0.5) × 104 M⊙ 的初始质量。这意味着 NGC 2112 可能已经损失了超过 90\%$ 的初始质量。根据获得的距离和运动学数据,我们还计算了星团的银河轨道。}}8} \pm {0{^{\prime }_{.}}2}$(∼1.5 个)。这表明 NGC 2112 的中心浓度参数为 C = log (Rcl/Rc) ∼ 0.92,比之前认为的要大得多。此外,我们估计星团的总质量 Mcl = 858 ± 12 M⊙ 和 Mini = (2.2 ± 0.5) × 104 M⊙ 的初始质量。这意味着 NGC 2112 可能已经损失了超过 90\%$ 的初始质量。根据获得的距离和运动学数据,我们还计算了星团的银河轨道。这意味着 NGC 2112 可能已经损失了超过 90\%$ 的初始质量。根据获得的距离和运动学数据,我们还计算了星团的银河轨道。这意味着 NGC 2112 可能已经损失了超过 90\%$ 的初始质量。根据获得的距离和运动学数据,我们还计算了星团的银河轨道。
更新日期:2021-04-10
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