HIGH ATOMIC CARBON ABUNDANCE IN MOLECULAR CLOUDS IN THE GALACTIC CENTER REGION
HIGH ATOMIC CARBON ABUNDANCE IN MOLECULAR CLOUDS IN THE GALACTIC CENTER REGION
复制标题
银河系中心区域分子云中的高原子碳丰度
DOI：
10.1088/2041-8205/743/2/l39
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
K. Kamegai
中科院分区：
文献类型：
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作者：
Kunihiko Tanaka;T. Oka;S. Matsumura;M. Nagai;K. Kamegai
这封信展示了一张奈奎斯特采样的高分辨率[C i] 3P1 - 3P0图，它是用阿塔卡马亚毫米望远镜实验10米望远镜拍摄的中央分子区（CMZ）的− 0. ° 2 <l <1. ° 2 × − 0. ° 1 <B <0 °区域。我们发现CMZ中的分子云可以根据它们的[Ci]/13CO强度比分为两组：一组是由具有低的、均匀的[Ci]/13CO比（0.45）的云组成的大块云，另一组是由具有高的[Ci]/13CO比（> 0.8）的云组成的大块云。[C i]增强区出现在M − 0.02 − 0.07、环核盘、180 pc环和高速致密云CO +0.02 − 0.02。我们进行了大的速度梯度分析，得出了M − 0.02 − 0.07的C0/CO柱密度比为0.47，大约是CMZ的体成分（0.26）的两倍。我们对M − 0.02 − 0.07的高C0丰度的起源提出了几个假设，包括宇宙射线/X射线离解和预先存在的分子云中CO的机械离解。我们还提出M − 0.02 − 0.07可能是一个处于扩散气体化学演化早期阶段的云，它可能是由银河系中心区域的棒诱导质量流入形成的。
This Letter presents a Nyquist-sampled, high-resolution [C i] 3P1–3P0 map of the −0.°2 < l < 1.°2 × −0.°1 < b < 0° region in the Central Molecular Zone (CMZ) taken with the Atacama Submillimeter Telescope Experiment 10 m telescope. We have found that molecular clouds in the CMZ can be classified into two groups according to their [C i]/13CO intensity ratios: a bulk component consisting of clouds with a low, uniform [C i]/13CO ratio (0.45) and another component consisting of clouds with high [C i]/13CO ratios (>0.8). The [C i]-enhanced regions appear in M−0.02−0.07, the circumnuclear disk, the 180 pc ring, and the high-velocity compact cloud CO+0.02−0.02. We have carried out a large velocity gradient analysis and have derived the C0/CO column density ratio for M−0.02−0.07 as 0.47, which is approximately twice that of the bulk component of the CMZ (0.26). We propose several hypotheses on the origin of high C0 abundance in M−0.02−0.07, including cosmic-ray/X-ray dissociation and mechanical dissociation of CO in the pre-existing molecular clouds. We also suggest the possibility that M−0.02−0.07 is a cloud at an early stage of chemical evolution from diffuse gas, which was possibly formed by the bar-induced mass inflow in the Galactic center region.