大麦云星云中年轻恒星天体的星际环境的HST观点
An HST View of the Interstellar Environments of Young Stellar Objects in the Large Magellanic Cloud
摘要：
我们已经使用档案HST H $α$图像来研究大质量和中等质量的年轻恒星对象（YSO）的候选人在大麦云（LMC）的直接环境。从Gruendl & Chu（2009）中选取的YSO候选样本是基于斯皮策IRAC和MIPS对整个LMC的观测以及补充的地面光学和近红外观测。我们在大麦哲伦星云中发现了99个YSO候选者的HST H $α$图像，其中82个似乎是真正的YSO。超过95%的YSO被发现与分子云有关。在H $α$图像中，YSO出现在三种不同的环境中：在乌云中，在明亮边缘的尘埃柱内部或尖端，以及在小的H II区域。在这三种不同的环境中的YSO的光谱能量分布的比较表明，YSO在暗云是最年轻的，YSO与小H II区域是最进化的，和YSO在明亮的边缘尘埃柱跨越一系列的中间进化阶段。这个粗略的演化序列证实了存在的硅酸盐吸收功能的斯皮策IRS光谱中的一些YSO在乌云和明亮的边缘尘埃柱，但不是那些YSO在小H II地区。我们提出了一个讨论触发恒星形成的YSO在明亮的边缘尘埃柱或在黑暗的云层邻近H II地区。在高分辨率HST图像中，多达50%的YSO被分解为多个源。这说明了使用高分辨率图像来探测大麦哲伦星云中YSO的真实性质和物理特性的重要性。
英文摘要：
We have used archival HST H$α$ images to study the immediate environments of massive and intermediate-mass young stellar object (YSO) candidates in the Large Magellanic Cloud (LMC). The sample of YSO candidates, taken from Gruendl & Chu (2009), was selected based on Spitzer IRAC and MIPS observations of the entire LMC and complementary ground-based optical and near-infrared observations. We found HST H$α$ images for 99 YSO candidates in the LMC, of which 82 appear to be genuine YSOs. More than 95% of the YSOs are found to be associated with molecular clouds. YSOs are seen in three different kinds of environments in the H$α$ images: in dark clouds, inside or on the tip of bright-rimmed dust pillars, and in small H II regions. Comparisons of spectral energy distributions for YSOs in these three different kinds of environments suggest that YSOs in dark clouds are the youngest, YSOs with small H II regions are the most evolved, and YSOs in bright-rimmed dust pillars span a range of intermediate evolutionary stages. This rough evolutionary sequence is substantiated by the presence of silicate absorption features in the Spitzer IRS spectra of some YSOs in dark clouds and in bright-rimmed dust pillars, but not those of YSOs in small H II regions. We present a discussion on triggered star formation for YSOs in bright-rimmed dust pillars or in dark clouds adjacent to H II regions. As many as 50% of the YSOs are resolved into multiple sources in high-resolution HST images. This illustrates the importance of using high-resolution images to probe the true nature and physical properties of YSOs in the LMC.
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