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arXiv 1601.04783astro-ph.GAastro-ph.SR
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与普朗克银河系冷团有关的分子核中的稠密气体

Dense gas in molecular cores associated with Planck Galactic cold clumps

Jinghua Yuan, Yuefang Wu, Tie Liu, Tianwei Zhang, Jin Zeng Li, Hong-Li Liu, Fanyi Meng, Ping Chen, Runjie Hu, Ke Wang

摘要:

我们提出了第一次调查稠密气体朝向普朗克银河系冷团(PGCC)。利用紫金山天文台13.7米望远镜对621个与PGCC有关的分子核进行了HCO+和HCN的J=1-0跃迁观测。其中,250个来源有检测,其中HCO+检测到230个核心,HCN检测到158个核心。从先前的映射观测中提取250个岩心中心的CO、13 CO和C18 O的J=1-0跃迁光谱,以构建多线数据集。非对称双峰轮廓的显著低的检测率,以及CO,HCO+和HCN光谱的中心速度之间的一致性,表明CO选择的普朗克核心比经典的恒星形成区域更安静。C18 O和HCN的线宽之间的小差异表明,CO选择的普朗克核心的内部区域并不比外部更动荡。HCO+的速度积分强度和丰度与HCN的正相关,表明这两个物种是很好的耦合和化学连接。探测到的HCO+和HCN的丰度明显低于其他低质量到高质量恒星形成区的值。低丰度可能是由于光束稀释。根据对PGCC星表中给出的参数的检验,我们认为可能有大约1000个PGCC天体具有足够的致密气体形成恒星的储备。

英文摘要:

We present the first survey of dense gas towards Planck Galactic Cold Clumps (PGCCs). Observations in the J=1-0 transitions of HCO+ and HCN towards 621 molecular cores associated with PGCCs were performed using the Purple Mountain Observatory 13.7-m telescope. Among them, 250 sources have detection, including 230 cores detected in HCO+ and 158 in HCN. Spectra of the J=1-0 transitions from CO, 13CO, and C18O at the centers of the 250 cores were extracted from previous mapping observations to construct a multi-line data set. The significantly low detection rate of asymmetric double-peaked profiles, together with the well consistence among central velocities of CO, HCO+, and HCN spectra, suggests that the CO-selected Planck cores are more quiescent compared to classical star-forming regions. The small difference between line widths of C18O and HCN indicates that the inner regions of CO-selected Planck cores are not more turbulent than the exterior. The velocity-integrated intensities and abundances of HCO+ are positively correlated with those of HCN, suggesting these two species are well coupled and chemically connected. The detected abundances of both HCO+ and HCN are significantly lower than values in other low- to high-mass star-forming regions. The low abundances may be due to beam dilution. On the basis of the inspection of the parameters given in the PGCC catalog, we suggest that there may be about 1 000 PGCC objects having sufficient reservoir of dense gas to form stars.

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