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arXiv 1111.4029astro-ph.GA
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银河系中心区分子云中的高原子碳丰度

High Atomic Carbon Abundance in Molecular Clouds in the Galactic Center Region

Kunihiko Tanaka, Tomoharu Oka, Shinji Matsumura, Makoto Nagai, Kazuhisa Kamegai

摘要:

这封信介绍了一个奈奎斯特采样的高分辨率[CI] 3 P1 - 3 P0地图,该地图是用阿塔卡马亚毫米望远镜实验(ASTE)10米望远镜拍摄的中央分子区(CMZ)的-0.2 deg < l < 1.2 deg x -0.1 deg < b < 0 deg区域。我们发现CMZ中的分子云可以根据它们的[CI]/13 CO强度比分为两组:一组是由具有低的、均匀的[CI]/13 CO比(0.45)的云组成的大块云,另一组是由具有高的[CI]/13 CO比(> 0.8)的云组成的大块云。[CI]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。我们进行了大速度梯度(LVG)分析,得出M-0.02-0.07的C^0/CO柱密度比为0.47,约为CMZ主体组分密度比(0.26)的两倍。我们对M-0.02-0.07中高C^0丰度的起源提出了几种假说,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可能是由扩散气体化学演化的早期阶段的云,它可能是由银河系中心区域的棒诱导质量流入形成的。

英文摘要:

This letter presents a Nyquist-sampled, high-resolution [CI] 3P1-3P0 map of the -0.2 deg < l < 1.2 deg x -0.1 deg < b < 0 deg region in the Central Molecular Zone (CMZ) taken with the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope. We have found that molecular clouds in the CMZ can be classified into two groups according to their [CI]/13CO intensity ratios: a bulk component consisting with clouds with a low, uniform [CI]/13CO ratio (0.45) and another component consisting of clouds with high [CI]/13CO ratios (> 0.8). The [CI]-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 (LVG) analysis and have derived the C^0/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 C^0 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.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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