arXiv 2202.015992022-02astro-ph.GAastro-ph.HE

恒星墓地：球状星团NGC 3201和NGC 6397中致密天体的成簇

Stellar graveyards: Clustering of compact objects in globular clusters NGC 3201 and NGC 6397

Eduardo Vitral, Kyle Kremer, Mattia Libralato, Gary A. Mamon, Andrea Bellini

备注：: 28 pages, 16 figures, 4 tables, accepted for publication in MNRAS
DOI：: 10.1093/mnras/stac1337

摘要：

利用贝叶斯质量轨道模拟程序MAMPOSSt-PM，分析了核心坍缩和非核心坍缩的球状星团NGC 6397和NGC 3201的盖亚EDR 3和重新校准的HST自行数据。我们使用贝叶斯证据和现实的模拟数据集与AGAMA构建不同的质量模型之间进行选择。在我们的数据范围内，在这两个集群中，速度是一致的各向同性。我们在两个星团中都探测到了大约1000个太阳质量的暗中心质量（DCM）。我们的MAMPOSSt-PM拟合强烈倾向于NGC 6397中的扩展DCM，而在NGC 3201中只表现出轻微的偏好，其大小分别为集群有效半径的大约百分之一和百分之几。我们探索我们的结果背后的天体物理学与CMC蒙特卡罗N体代码，其快照最好的相空间观测匹配导致类似的值的DCM的质量和大小。因此，内部运动学与NGC 6397中数百颗大质量白矮星和NGC 3201中大约100个分离的恒星质量黑洞的人口一致，正如以前用CMC发现的那样。这些分析证实了质量轨道模型和蒙特卡罗N体技术的准确性，它们共同提供了对球状星团（核心坍缩与否）DCM的更可靠的预测。这为理解星团中大量有趣的天体物理现象提供了可能性，例如快速射电暴、致密天体合并和引力波。

英文摘要：

We analyse Gaia EDR3 and re-calibrated HST proper motion data from the core-collapsed and non core-collapsed globular clusters NGC 6397 and NGC 3201, respectively, with the Bayesian mass-orbit modelling code MAMPOSSt-PM. We use Bayesian evidence and realistic mock data sets constructed with AGAMA to select between different mass models. In both clusters, the velocities are consistent with isotropy within the extent of our data. We robustly detect a dark central mass (DCM) of roughly 1000 solar masses in both clusters. Our MAMPOSSt-PM fits strongly prefer an extended DCM in NGC 6397, while only presenting a mild preference for it in NGC 3201, with respective sizes of a roughly one and a few per cent of the cluster effective radius. We explore the astrophysics behind our results with the CMC Monte Carlo N-body code, whose snapshots best matching the phase space observations lead to similar values for the mass and size of the DCM. The internal kinematics are thus consistent with a population of hundreds of massive white dwarfs in NGC 6397, and roughly 100 segregated stellar-mass black holes in NGC 3201, as previously found with CMC. Such analyses confirm the accuracy of both mass-orbit modelling and Monte Carlo N-body techniques, which together provide more robust predictions on the DCM of globular clusters (core-collapsed or not). This opens possibilities to understand a vast range of interesting astrophysical phenomena in clusters, such as fast radio bursts, compact object mergers, and gravitational waves.

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