论文标题
在低金属环境中，年轻簇的质量功能。 SH 2-209
Mass function of a young cluster in a low-metallicity environment. Sh 2-209
论文作者
论文摘要
我们介绍了SH 2-209（S209）的深近红外（NIR）成像，这是一个低金属性（$ {\ rm [o/h]} = -0.5 $ dex）HII区域中的HII区域。从NIR图像中，结合Gaia EDR3的天文数据，我们估计距离S209的距离为2.5 kpc。这足够近，可以使我们能够清楚地解决群集成员（$ \ simeq $ 1000 au分离）至$ \ simeq $ 0.1 $ m_ \ odot $的质量检测极限，我们已经确定了S209中的两个星形形成簇，并具有单独的群集量表$ \ sim $ \ sim $ \ sim $ 1p。我们采用一组模型光度函数来得出两个簇的基本初始质量函数（IMF）和年龄。与Salpeter IMF（$γ= -1.35 $）相比，我们获得的两个簇获得的IMF均表现出略平坦的高质量斜率（$γ\ simeq -1.0 $），并且它们的断裂质量为$ \ simeq $ 0.1 $ m_ \ odot $比Solar $ \ sim $ \ sim $ 0.3 $ \ m_ py y sim $ \ odot $低。特别是，由于S209主聚类是一个星形群集，比以前在此类环境中研究的区域中的数量（$ \ sim $ 1500）的数量（$ \ sim $ 1500）（$ \ sim $ 1500），因此首次有可能在低水平环境中首次在低水平环境中获得IMF，而高于质量的0.1--20--20-20 $ m_ \ m_ \ osot $ \ osot均可获得高度准确的范围。
We present deep near-infrared (NIR) imaging of Sh 2-209 (S209), a low-metallicity (${\rm [O/H]} = - 0.5$ dex) HII region in the Galaxy. From the NIR images, combined with astrometric data from Gaia EDR3, we estimate the distance to S209 to be 2.5 kpc. This is close enough to enable us to resolve cluster members clearly ($\simeq$1000 AU separation) down to a mass-detection limit of $\simeq$0.1 $M_\odot$, and we have identified two star-forming clusters in S209, with individual cluster scales $\sim$1 pc. We employ a set of model luminosity functions to derive the underlying initial mass functions (IMFs) and ages for both clusters. The IMFs we obtained for both clusters exhibit slightly flat high-mass slopes ($Γ\simeq -1.0$) compared to the Salpeter IMF ($Γ= -1.35$), and their break mass of $\simeq$0.1 $M_\odot$ is lower than those generally seen in the solar neighborhood ($\sim$0.3 $M_\odot$). In particular, because the S209 main cluster is a star-forming cluster with a larger number of members ($\sim$1500) than the number ($\sim$100) in regions previously studied in such environments, it is possible for the first time to derive the IMF in a low-metallicity environment with high accuracy over the wide mass range 0.1--20 $M_\odot$.
