论文标题

燃气后,年轻恒星群的不同命运

Different Fates of Young Star Clusters After Gas Expulsion

论文作者

Pang, Xiaoying, Li, Yuqian, Tang, Shih-Yun, Pasquato, Mario, Kouwenhoven, M. B. N.

论文摘要

我们在太阳能社区(323.0 PC)和新发现的Star Cluster LP 2439(289.1 PC)中确定了年轻星团NGC 2232的结构。使用无监督的机器学习方法\ textsc {stargo}使用GAIA DR2 SKY位置,视差和适当的运动数据来确定成员候选者。使用颜色级图进一步去除了来自银河磁盘的成员污染。恒星的四个已鉴定组(NGC 2232,LP 2439和两个丝状结构)是同时的,年龄为25 MYR,很可能在同一巨型分子云中形成。我们使用贝叶斯方法纠正与视差误差的距离不对称性。 3D形态显示了簇NGC 2232和LP 2439的两个球形分布。两个丝状结构在空间上是在空间上,并且运动学上连接到NGC 2232。NGC 2232和LP 2439都在扩展。在LP 2439中,该扩展更为重要,产生了较浅的空间分布,其体积数和质量密度曲线较浅。该扩展被认为主要是由燃气驱动驱动的。 NGC 2232,占群集质量的73%,目前正在经历重新验证的过程,但是,LP 2439(52%的群集质量都没有结合,可能会在不久的将来完全溶解。不同的生存能力在驱逐出气体发作之前,迹象的NGC 2232和LP 2439的不同动力学状态。 NGC 2232可能已经进行了次要结构和次病毒,而LP 2439可能是病毒/监管,或者经历了清除气体的速度要快得多。

We identify structures of the young star cluster NGC 2232 in the solar neighborhood (323.0 pc), and a newly discovered star cluster LP 2439 (289.1 pc). Member candidates are identified using the Gaia DR2 sky position, parallax and proper motion data, by an unsupervised machine learning method, \textsc{StarGO}. Member contamination from the Galactic disk is further removed using the color magnitude diagram. The four identified groups (NGC 2232, LP 2439 and two filamentary structures) of stars are coeval with an age of 25 Myr and were likely formed in the same giant molecular cloud. We correct the distance asymmetry from the parallax error with a Bayesian method. The 3D morphology shows the two spherical distributions of clusters NGC 2232 and LP 2439. Two filamentary structures are spatially and kinematically connected to NGC 2232. Both NGC 2232 and LP 2439 are expanding. The expansion is more significant in LP 2439, generating a loose spatial distribution with shallow volume number and mass density profiles. The expansion is suggested to be mainly driven by gas expulsion. NGC 2232, with 73~percent of the cluster mass bound, is currently experiencing a process of re-virialization, However, LP 2439, with 52 percent cluster mass being unbound, may fully dissolve in the near future. The different survivability traces different dynamical states of NGC 2232 and LP 2439 prior to the onset of gas expulsion. NGC 2232 may have been substructured and subvirial, while LP 2439 may either have been virial/supervirial, or it has experienced a much faster rate of gas removal.

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