论文标题

在外部银河系中,在两个远处的恒星形成IRA 22147+5948的年轻恒星物体的人口普查中

A census of young stellar objects in two line-of-sight star forming regions toward IRAS 22147+5948 in the outer Galaxy

论文作者

Karska, Agata, Koprowski, Maciej, Solarz, Aleksandra, Szczerba, Ryszard, Sewiło, Marta, Siódmiak, Natasza, Elia, Davide, Gawroński, Marcin, Grzesiak, Konrad, Yung, Bosco H. K., Fischer, William J., Kristensen, Lars E.

论文摘要

(删节的)外星系中的恒星形成,即在太阳圆外的外部,部分是由于与负金属性梯度相关的分子云的低CO亮度。最近的红外调查概述了银河系大部分的灰尘发射,但在远红外波长下遭受了云混乱和空间分辨率不佳。我们旨在开发一种方法,以识别和分类外部星系中星形区域中的年轻恒星对象(YSO),并使用它来解决IRAS 22147+5948的距离和进化状态的长期混乱。我们使用支持矢量机学习算法来补充标准的颜色色和颜色刻度图,以搜索IRAS 22147区域中的YSO,并使用“外部星系的Spitzer映射”调查中的公共可用数据。凝聚力分层聚类算法用于识别簇,以及Robitaille等人。 (2017)计算单个YSO的物理特性的代码。我们使用颜色图分别使用机器学习技术来确定13类I类和13类II类YSO候选者,并分别使用2和21个来源。用星和被动磁盘对23个来源的光谱能分布进行建模,与II类对象相对应。 3个来源的模型包括I类对象的典型信封。将对象分组为位于〜2.2 kpc的距离的2个簇中,在〜5.6 kpc处分组5个簇。 CO,无线电连续体和灰尘发射的空间范围证实了沿着相似的视线沿两个不同星形成区域中YSO的起源。外部星系可能是跨环境中恒星形成的独特实验室,条件是互补方法和辅助数据可用于正确说明云混乱和距离不确定性。

(abridged) Star formation in the outer Galaxy, i.e., outside of the Solar circle, has been lightly studied in part due to low CO brightness of molecular clouds linked with the negative metallicity gradient. Recent infrared surveys provide an overview of dust emission in large sections of the Galaxy, but suffer from cloud confusion and poor spatial resolution at far-infrared wavelengths. We aim to develop a methodology to identify and classify young stellar objects (YSOs) in star-forming regions in the outer Galaxy, and use it to solve a long-standing confusion with the distance and evolutionary status of IRAS 22147+5948. We use Support Vector Machine learning algorithm to complement standard color-color and color-magnitude diagrams in search for YSOs in the IRAS 22147 region using publicly available data from the `Spitzer Mapping of the Outer Galaxy' survey. The agglomerative hierarchical clustering algorithm is used to identify clusters, along with the Robitaille et al. (2017) code to calculate physical properties of individual YSOs. We identify 13 Class I and 13 Class II YSO candidates using the color-color diagrams, and additional 2 and 21 sources, respectively, using the machine learning techniques. Spectral energy distributions of 23 sources are modelled with a star and a passive disk, corresponding to Class II objects. Models of 3 sources include envelopes typical for Class I objects. The objects are grouped in 2 clusters located at the distance of ~2.2 kpc, and 5 clusters at ~5.6 kpc. The spatial extent of CO, radio continuum, and dust emission confirms the origin of YSOs in two distinct star-forming regions along a similar line-of-sight. The outer Galaxy might serve as a unique laboratory of star formation across environments on condition that complementary methods and ancillary data are used to properly account for cloud confusion and distance uncertainties.

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