The Massive Stellar Population of W49: A Spectroscopic Survey
The Massive Stellar Population of W49: A Spectroscopic Survey
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DOI：
10.1051/0004-6361/201527823
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发表时间：
2013-07
期刊：
影响因子：
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通讯作者：
Shi-wei Wu;A. Bik;J. Bestenlehner;T. Henning;A. Pasquali;W. Brandner;A. Stolte
中科院分区：
文献类型：
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作者：
Shi-wei Wu;A. Bik;J. Bestenlehner;T. Henning;A. Pasquali;W. Brandner;A. Stolte
大质量恒星形成的尺度不同，从大而分散的OB星团到紧凑而密集的星暴星团。大质量恒星形成区域的复杂结构和所涉及的短时间尺度对我们理解它们的诞生和早期演化提出了挑战。作为银河系中质量最大、最明亮的恒星形成区之一，W49是研究大质量恒星形成的理想场所。通过对深嵌在W49分子云中的大质量年轻恒星进行分类，我们旨在研究和追踪该区域的恒星形成历史。我们结合NTT/SOFI和LBT/LUCI获得的$JHK$图像，分析了LBT/LUCI对W49的近红外$K$波段光谱观测结果。基于$JHK$波段测光和k波段光谱学，大质量恒星被放置在赫茨普龙罗素图中。通过与演化模型的比较，可以研究它们的年龄以及W49的恒星形成历史。我们的光谱调查确定了14颗O型恒星和2颗年轻恒星天体（yso）。11颗o星是主序星，其亚型从O3到O9.5不等，质量从$\sim 20$$M_{\odot}$到$\sim 120$$M_{\odot}$不等。其中三颗o型恒星表现出强烈的风特征，被认为是质量超过100的of型超巨星$M_{\odot}$。这两个yso显示出CO的排放，表明在大质量星团的中心区域存在星周盘。该星团的年龄估计为$\sim1.5$ Myr，在该区域的不同部分仍在形成恒星。来自中心大质量恒星的电离光子还没有清除围绕在星团周围的分子茧。W49与河外恒星形成区相当，为我们提供了详细研究星暴的独特可能性。
Massive stars form on different scales ranging from large, dispersed OB associations to compact, dense starburst clusters. The complex structure of regions of massive star formation, and the involved short timescales provide a challenge for our understanding of their birth and early evolution. As one of the most massive and luminous star-forming region in our Galaxy, W49 is the ideal place to study the formation of the most massive stars. By classifying the massive young stars deeply embedded into the molecular cloud of W49, we aim to investigate and trace the star formation history of this region. We analyse near-infrared $K$-band spectroscopic observations of W49 from LBT/LUCI combined with $JHK$ images obtained with NTT/SOFI and LBT/LUCI. Based on $JHK$-band photometry and K-band spectroscopy the massive stars are placed in a Hertzsprung Russell diagram. By comparison with evolutionary models, their age and hence the star formation history of W49 can be investigated. Fourteen O type stars as well as two young stellar objects (YSOs) are identified by our spectroscopic survey. Eleven O-stars are main sequence stars with subtypes ranging from O3 to O9.5, with masses ranging from $\sim 20$ $M_{\odot}$ to $\sim 120$ $M_{\odot}$. Three of the O-stars show strong wind features, and are considered to be Of-type supergiants with masses beyond 100 $M_{\odot}$ . The two YSOs show CO emission, indicative for the presence of circumstellar disks in the central region of the massive cluster. The age of the cluster is estimated as $\sim1.5$ Myr, with star formation still ongoing in different parts of the region. The ionising photons from the central massive stars have not yet cleared the molecular cocoon surrounding the cluster. W49 is comparable to extragalactic star-forming regions and provides us with an unique possibility to study a starburst in detail.