arXiv 2307.030352023-07-06astro-ph.GA

利用无监督机器学习发现来自半人马座ω的潮汐碎片

Tidal debris from Omega Centauri discovered with unsupervised machine learning

Kris Youakim, Karin Lind, Iryna Kushniruk

备注：: 22 pages, 19 figures, 2 tables, accepted for publication in MNRAS
DOI：: 10.1093/mnras/stad1952

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AI总结：

本文利用GALAH DR3和Gaia eDR3高维数据及无监督机器学习，在半人马座ω周围发现延伸超过50°的潮汐剥离候选恒星，并通过模拟恒星流约束其吸积时间下限，支持其为瓦解矮星系残余核心。

摘要：

银河系与落入卫星之间的引力相互作用提供了关于我们星系形成和演化的丰富信息。本文中，我们利用GALAH DR3与Gaia eDR3数据集的高维特性，来识别邻近星团半人马座ω（ω Cen）新的潮汐剥离候选恒星。我们同时研究化学和动力学参数空间，并在主星团体外空间分离的区域中识别星团候选体，这些区域受到晕场星的污染较高。最值得注意的是，我们发现ω Cen的候选体散布在晕中，延伸至距离星团主体超过50°的地方。利用以类似ω Cen轨道性质生成的模拟恒星流网格，我们将这些候选体的天空分布与模型进行比较。结果表明，如果ω Cen的初始质量与其当前质量相似，那么我们可以对其吸积时间设定一个下限，即t_acc > 70亿年前。或者，如果初始恒星质量显著更大，正如ω Cen是矮星系残余核心所预期的那样，那么我们可以将吸积时间限制为t_acc > 40亿年前。综合来看，这些结果与ω Cen是一个被瓦解的矮星系残余核心的情景一致。

英文摘要：

The gravitational interactions between the Milky Way and in-falling satellites offer a wealth of information about the formation and evolution of our Galaxy. In this paper, we explore the high-dimensionality of the GALAH DR3 plus Gaia eDR3 data set to identify new tidally stripped candidate stars of the nearby star cluster Omega Centauri ($ω\,\mathrm{Cen}$). We investigate both the chemical and dynamical parameter space simultaneously, and identify cluster candidates that are spatially separated from the main cluster body, in regions where contamination by halo field stars is high. Most notably, we find candidates for $ω\,\mathrm{Cen}$ scattered in the halo extending to more than $50^{\circ}$ away from the main body of the cluster. Using a grid of simulated stellar streams generated with $ω\,\mathrm{Cen}$ like orbital properties, we then compare the on sky distribution of these candidates to the models. The results suggest that if $ω\,\mathrm{Cen}$ had a similar initial mass as its present day mass, then we can place a lower limit on its time of accretion at t$_{\mathrm{acc}} > 7$ Gyr ago. Alternatively, if the initial stellar mass was significantly larger, as would be expected if $ω\,\mathrm{Cen}$ is the remnant core of a dwarf Galaxy, then we can constrain the accretion time to t$_{\mathrm{acc}} > 4$ Gyr ago. Taken together, these results are consistent with the scenario that $ω\,\mathrm{Cen}$ is the remnant core of a disrupted dwarf galaxy.

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