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arXiv 0706.3583astro-ph
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大质量红外暗云的外流和稠密气体发射

Outflow and dense gas emission from massive Infrared Dark Clouds

H. Beuther, T. K. Sridharan

摘要:

红外暗云预计在不同的,非常年轻的进化阶段的港口来源。为了更好地描述这些差异,我们观察了43个大质量红外暗云的样本,最初被选为候选的高质量无星核心,IRAM 30米望远镜覆盖低密度气体,高密度气体,分子流出/喷流和温度效应的谱线示踪剂。SiO(2-1)观测揭示了对18个源的探测。假设一氧化硅完全是由尘埃颗粒溅射产生的,这意味着至少有40%的样本恒星正在形成。观察到一个广泛的SiO线宽(2.2和65公里/秒之间),我们讨论了这种速度传播的潜在起源。虽然低密度示踪剂12 CO(2-1)和13 CO(1-0)在几个速度分量中被检测到,但高密度示踪剂H13 CO+(1- 0)通常仅显示单个速度分量,因此非常适合于IRDC的运动学距离估计。此外,H13 CO+的线宽平均比以前观察到的NH3(1,1)的线宽大1.5倍。这表明在致密的核心中心有更多的运动,这可能是由于湍流或开始恒星形成活动。此外,我们只检测到6个来源的CH 3CN,而CH 3OH被观察到约40%的样品。甲烷氯化萘和甲烷OH丰度的估计值较低,平均值分别为1.2x10^{-10}和4.3x10^{-10}。这些结果与高质量恒星形成的最早演化阶段的化学模型是一致的。此外,CH 3OH丰度与最近报道的低质量无星核的值相比也很好。

英文摘要:

Infrared Dark Clouds are expected to harbor sources in different, very young evolutionary stages. To better characterize these differences, we observed a sample of 43 massive Infrared Dark Clouds, originally selected as candidate high-mass starless cores, with the IRAM 30m telescope covering spectral line tracers of low-density gas, high-density gas, molecular outflows/jets and temperature effects. The SiO(2-1) observations reveal detections toward 18 sources. Assuming that SiO is exclusively produced by sputtering from dust grains, this implies that at least in 40% of this sample star formation is on-going. A broad range of SiO line-widths is observed (between 2.2 and 65km/s), and we discuss potential origins for this velocity spread. While the low-density tracers 12CO(2-1) and 13CO(1-0) are detected in several velocity components, the high-density tracer H13CO+(1--0) generally shows only a single velocity component and is hence well suited for kinematic distance estimates of IRDCs. Furthermore, the H13CO+ line-width is on average 1.5 times larger than that of previously observed NH3(1,1). This is indicative of more motion at the denser core centers, either due to turbulence or beginning star formation activity. In addition, we detect CH3CN toward only six sources whereas CH3OH is observed toward approximately 40% of the sample. Estimates of the CH3CN and CH3OH abundances are low with average values of 1.2x10^{-10} and 4.3x10^{-10}, respectively. These results are consistent with chemical models at the earliest evolutionary stages of high-mass star formation. Furthermore, the CH3OH abundances compare well to recently reported values for low-mass starless cores.

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