剑鱼座30中发现一颗年轻的大质量嵌入恒星的致密分子云
Discovery of a dense molecular cloud towards a young massive embedded star in 30 Doradus
摘要：
大麦云星云中的剑鱼座30区是本星系群中最突出的恒星形成区之一，也是研究低金属环境下恒星形成的主要目标。为了获得尚未消耗或分散的冷气体的更完整的图片，我们搜索了分子云的线发射，这可能与该地区检测到的分子氢发射有关。我们用15米SEST望远镜获得了高灵敏度的12 CO J=2-1图，并辅以13 CO J=2-1和CS J=2-1的定点观测。我们报告了在R136西北方向约20”（约5 pc，距离50 kpc）处发现了一个密集的分子云，这是一个紧凑的大质量中央星团，为LMC中的剑鱼座30提供动力，这可能会引发周围分子云中的恒星形成。我们推导出的分子质量$\lesssim 10^4$ \msol，3 pc的线性半径，作为上限，和$\gtrsim 10^{3}$ cm $^{-3}$的云的平均密度。CS J=2-1发射谱线的检测指示较大的密度，$\sim 10^{6}$ cm $^{-3}$。致密的分子云与分子2.12 μ m H2发射有关。我们认为，所观察到的分子气体可能是致密分子物质的残留物，这些物质在年轻的大质量恒星形成的强紫外线场和风的作用下幸存下来。
英文摘要：
The 30 Doradus region in the Large Magellanic Cloud is one of the most outstanding star forming regions of the Local Group and a primary target to study star formation in an environment of low metallicity. In order to obtain a more complete picture of the not yet consumed or dispersed cool gas, we searched for line emission from molecular clouds that could be associated with molecular hydrogen emission detected in the region. We obtained a high sensitivity 12CO J=2-1 map with the 15-m SEST telescope, complemented by pointed observations of 13CO J=2-1 and CS J=2-1. We report the discovery of a dense molecular cloud towards an embedded young massive star at ~ 20" (~5 pc, at the distance of 50 kpc) northwest of R136, the compact massive central stellar cluster powering 30 Doradus in the LMC, that could be triggering star formation in the surrounding molecular clouds. We derived a molecular mass of $\lesssim 10^4$ \msol, a linear radius of 3 pc, as an upper limit, and a mean density of $\gtrsim 10^{3}$ cm$^{-3}$ for the cloud. The detection of CS J=2-1 emission line indicates larger densities, $\sim 10^{6}$ cm$^{-3}$. The dense molecular cloud is associated with molecular 2.12 um H2 emission. We suggest that the observed molecular gas could be the remains of dense molecular material surviving the action of strong UV fields and winds in which the young massive star has formed.
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