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arXiv 0905.3511astro-ph.SR
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在暗云中寻找富含碳链的核心

A Search for Carbon-Chain-Rich Cores in Dark Clouds

Tomoya Hirota, Masatoshi Ohishi, Satoshi Yamamoto

备注：
41 pages, 6 figures, accepted for publication in ApJ (July 2009, v700 issue)
发表信息：
Astrophys.J.699:585-602,2009
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摘要：

我们目前的调查结果CCS，HC $_{3}$ N，HC $_{5}$ N对40个暗云核心，以寻找“碳链-生产区（CCPR）"，在那里的碳链分子是非常丰富的相对于NH $_{3}$，如在L1495 B，L1521 B，L1521 E，和TMC-1的氰基多炔峰。我们主要观察到NH $_{3}$线较弱、未检测到或在以前的调查中未观察到的岩心，CCS、HC $_{3}$ N和HC $_{5}$ N线分别在17、17和5个源中检测到。其中，我们已经发现了一个CCPR，L492，及其可能的候选者，L1517 D，L530 D，L1147和L1172 B。它们都显示出低的[NH $_{3}$ ]/[CCS]丰度比（以下称为NH $_{3}$ /CCS比），表明化学年轻。结合我们的结果与以前的调查，我们发现了一个显着的变化的NH $_{3}$ /CCS的比之间的暗云核和分子云复合体。碳链分子的检测率也表明了这种变化。例如，NH $_{3}$ /CCS的比率较高，碳链分子的检测率较低的蛇夫座核心比金牛座核心。这些系统的丰度变化的起源进行了讨论的演化阶段或收缩时标的差异。我们还发现了一个富含碳链的恒星形成核心L483，在那里检测到了强烈的HC $_{3}$ N和HC $_{5}$ N线。这是一个可能的候选核心与“温暖的碳链化学”。

英文摘要：

We present results of a survey of CCS, HC$_{3}$N, and HC$_{5}$N toward 40 dark cloud cores to search for "Carbon-Chain--Producing Regions(CCPRs)", where carbon-chain molecules are extremely abundant relative to NH$_{3}$, as in L1495B, L1521B, L1521E, and the cyanopolyyne peak of TMC-1. We have mainly observed toward cores where the NH$_{3}$ lines are weak, not detected, or not observed in previous surveys, and the CCS, HC$_{3}$N, and HC$_{5}$N lines have been detected toward 17, 17, and 5 sources, respectively. Among them, we have found a CCPR, L492, and its possible candidates, L1517D, L530D, L1147, and L1172B. They all show low abundance ratios of [NH$_{3}$]/[CCS] (hereafter called the NH$_{3}$/CCS ratio) indicating the chemical youth. Combining our results with those of previous surveys, we have found a significant variation of the NH$_{3}$/CCS ratio among dark cloud cores and among molecular cloud complexes. Such a variation is also suggested by the detection rates of carbon-chain molecules. For instance, the NH$_{3}$/CCS ratios are higher and the detection rates of carbon-chain molecules are lower in the Ophiuchus cores than in the Taurus cores. An origin of these systematic abundance variation is discussed in terms of the difference in the evolutionary stage or the contraction timescale. We have also identified a carbon-chain-rich star-forming core, L483, where intense HC$_{3}$N and HC$_{5}$N lines are detected. This is a possible candidate for a core with "Warm Carbon-Chain Chemistry".

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