论文标题

测量时空中的年轻恒星-II。 N44的序列前恒星含量

Measuring Young Stars in Space and Time -- II. The Pre-Main-Sequence Stellar Content of N44

论文作者

Ksoll, Victor F., Gouliermis, Dimitrios, Sabbi, Elena, Ryon, Jenna E., Robberto, Massimo, Gennaro, Mario, Klessen, Ralf S., Koethe, Ullrich, de Marchi, Guido, Chen, C. -H. Rosie, Cignoni, Michele, Dolphin, Andrew E.

论文摘要

测量时空中年轻恒星(MySST)的哈勃太空望远镜(HST)调查需要一些最深的光度观测值,即在大型麦芽云中捕获活跃星形成复合物N44的最低质量恒星。我们采用新的MySST恒星目录来识别和表征N44中年轻的预序列(PMS)星的含量,并分析PMS聚类结构。为了区分PMS恒星与更具进化的视线污染物,这是由于几种效果改变光度法而导致的一项不足的任务,我们使用了机器学习分类方法。这包括训练支持向量机(SVM)和随机森林(RF)在精心选择的MySST数据子集上,并将所有观察到的恒星归类为PMS或非PMS。将SVM和RF预测结合在一起,以检索最强大的PMS来源,我们发现N44的PMS概率高于95%的$ \ sim26,700 $候选人。我们采用基于最近的邻居表面密度估算的聚类方法,以$ 1 $ $σ$的意义在平均密度高于平均密度高的$ 1 $σ$中,子群体持续持续且超过$ 3 $σ$的意义。最活跃的星形形成中心位于N44泡泡的西部边缘,是一个子集群,有效半径为$ \ sim 5.6 $ PC,需要超过1,100 pms的候选人。此外,我们确认几乎所有确定的簇与已知的H II地区一致,并且靠近或携带众多的年轻O星或YSO,或者先前由Muse和Spitzer观测发现。

The Hubble Space Telescope (HST) survey Measuring Young Stars in Space and Time (MYSST) entails some of the deepest photometric observations of extragalactic star formation, capturing even the lowest mass stars of the active star-forming complex N44 in the Large Magellanic Cloud. We employ the new MYSST stellar catalog to identify and characterize the content of young pre-main-sequence (PMS) stars across N44 and analyze the PMS clustering structure. To distinguish PMS stars from more evolved line of sight contaminants, a non-trivial task due to several effects that alter photometry, we utilize a machine learning classification approach. This consists of training a support vector machine (SVM) and a random forest (RF) on a carefully selected subset of the MYSST data and categorize all observed stars as PMS or non-PMS. Combining SVM and RF predictions to retrieve the most robust set of PMS sources, we find $\sim26,700$ candidates with a PMS probability above 95% across N44. Employing a clustering approach based on a nearest neighbor surface density estimate, we identify 18 prominent PMS structures at $1$ $σ$ significance above the mean density with sub-clusters persisting up to and beyond $3$ $σ$ significance. The most active star-forming center, located at the western edge of N44's bubble, is a subcluster with an effective radius of $\sim 5.6$ pc entailing more than 1,100 PMS candidates. Furthermore, we confirm that almost all identified clusters coincide with known H II regions and are close to or harbor massive young O stars or YSOs previously discovered by MUSE and Spitzer observations.

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