大质量恒星形成中的乙炔基（C2H）：追踪初始条件？
Ethynyl (C2H) in massive star formation: Tracing the initial conditions?
摘要：
APEX单碟观测在亚毫米波长对大质量恒星形成区域的样本显示，C2H几乎无处不在，对所有覆盖的进化阶段，从红外暗云通过高质量原恒星物体超压缩HII地区。从亚毫米阵列对一个热核状大质量原恒星物体的高分辨率数据显示，C2H的壳状分布，半径约9000 AU的中心亚毫米峰位置周围。这些观察到的功能很好地再现了一个一维云模式与幂律密度和温度分布和气体颗粒化学网络。反应性的C2H自由基（乙炔基）在大质量恒星形成开始时是丰富的，但后来它迅速转化为核心中心的其他分子。在外层云区，C2H的丰度仍然很高，这是由于星际紫外光子从CO中解离出的元素碳不断补充。我们认为，C2H可能是一种非常适合研究大质量恒星形成的初始条件的分子。
英文摘要：
APEX single-dish observations at sub-millimeter wavelengths toward a sample of massive star-forming regions reveal that C2H is almost omni-present toward all covered evolutionary stages from Infrared Dark Clouds via High-Mass Protostellar Objects to Ultracompact HII regions. High-resolution data from the Submillimeter Array toward one hot-core like High-Mass Protostellar Object show a shell-like distribution of C2H with a radius of ~9000AU around the central submm peak position. These observed features are well reproduced by a 1D cloud model with power-law density and temperature distributions and a gas-grain chemical network. The reactive C2H radical (ethynyl) is abundant from the onset of massive star formation, but later it is rapidly transformed to other molecules in the core center. In the outer cloud regions the abundance of C2H remains high due to constant replenishment of elemental carbon from CO being dissociated by the interstellar UV photons. We suggest that C2H may be a molecule well suited to study the initial conditions of massive star formation.
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