超紧密HII区域G5周围的热团分子茧.89-0.39
The Hot and Clumpy Molecular Cocoon Surrounding the Ultracompact HII Region G5.89-0.39
摘要：
我们用亚毫米波阵列观测了CH_3CN（12-11）在壳状超紧HII区G5.89-0.39的发射，分辨率为2”。积分的CH 3CN发射揭示了在HII区域G5.89-0.39的外围的致密和热的分子茧，其中CH 3CN缺乏区域大致集中在G5.89-0.39处。通过分析的CH 3CN排放使用人口图分析，我们发现，第一次，从150到40 K的温度降低结构与从费尔特的恒星，这被认为是负责供电的HII区域的投影距离。我们的研究结果进一步表明，在所观察到的致密气体中的大部分热能是由费尔特星提供的。从导出的CH 3CN柱密度分布，我们得出结论，致密气体不是均匀分布的，而是集中的，当r < 8000 AU时，幂律指数为5.5，当8000 AU < r < 20000 AU时，幂律指数为2.0，其中r是到费尔特星的距离。估计的大功率指数为5.5，这可以归因于费尔特星附近CH 3CN丰度的增强。
英文摘要：
We present observations of CH3CN (12-11) emission at a resolution of 2" toward the shell-like ultracompact HII region G5.89-0.39 with the Submillimeter Array. The integrated CH3CN emission reveals dense and hot molecular cocoon in the periphery of the HII region G5.89-0.39, with a CH3CN deficient region roughly centered at G5.89-0.39. By analyzing the CH3CN emission using population diagram analysis, we find, for the first time, a decreasing temperature structure from 150 to 40 K with the projected distance from Feldt's star, which is thought to be responsible for powering the HII region. Our results further indicate that the majority of the heating energy in the observed dense gas is supplied by the Feldt's star. From the derived CH3CN column density profile, we conclude that the dense gas is not uniformly-distributed but centrally-concentrated, with a power-law exponent of 5.5 for r < 8000 AU, and 2.0 for 8000 AU < r < 20000 AU, where r is the distance to Feldt's star. The estimated large power index of 5.5 can be attributed to an enhancement of CH3CN abundance in the close vicinity of Feldt's star.
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