FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 mtelescope (FUGIN). Ⅶ. molecular fraction of HI clouds
FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 mtelescope (FUGIN). Ⅶ. molecular fraction of HI clouds
复制标题
使用 Nobeyama 45 望远镜 (FUGIN) 对 HI 云进行的无偏银河平面成像调查。
DOI：
10.1093/pasj/psaa027
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发表时间：
2020
影响因子：
2.3
通讯作者：
T.
中科院分区：
文献类型：
--
作者：
Nakanishi;H.;Fujita;S.;Tachihara;K.;Izumi;N.;Matsuo;M.;Umemoto;T.;Oasa;Y.;& Inoue;T.
我们分析分子气体形成中性原子氢（Hi）云使用最新的CO数据，从森林（45米望远镜上的四光束接收系统）无偏银河平面成像调查与Nobeyama 45米望远镜，并使用Hidata从甚大阵银河平面调查。我们对Hidata立方体应用了树状图算法来识别Hicloud，并通过对每个Hicloud内的CO谱线强度求和来计算Himass和分子气体质量。在此基础上，我们建立了一个包含5737个已识别的Hiclouds的星表，其地方静止速度标准（LSR）≤ −20 km s− 1，经度范围为20° ≤l≤ 50°，纬度范围为−1° ≤B≤ 1°。我们发现，大多数的雾云分布在银河中心距离16千秒差距，其中大部分是在冷中性的中间阶段。此外，我们确定了Himass函数的高质量端与指数为2.3的幂律函数拟合得很好。虽然两个序列的自引力云和扩散云预计将出现在thetot图根据以前的作品的基础上的平面平行模式，观测数据显示，只有一个单一的序列与大的散射在这两个序列。这意味着大多数云是这两种云的混合物。此外，我们提出了以下的分子气体形成的情况下：一个高占主导地位的云演变与增加H2质量沿着的路径，通过收集扩散气体之前，达到和移动沿着曲线的两个序列。
We analyze molecular-gas formation in neutral atomic hydrogen (Hi) clouds using the latest CO data, obtained from the FOREST (four-beam receiver system on the 45 m telescope) unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope, and using Hidata taken from the Very Large Array Galactic plane survey. We applied a dendrogram algorithm to the Hidata cube to identify Hiclouds, and we calculated the Himass and molecular-gas mass by summing the CO line intensity within each Hicloud. On the basis of the results, we created a catalog of 5737 identified Hiclouds with local standard of rest (LSR) velocity ofVLSR≤ −20 km s−1in galactic longitude and latitude ranges of 20° ≤l≤ 50° and −1° ≤b≤ 1°, respectively. We found that most of the Hiclouds are distributed within a Galactocentric distance of 16 kpc, and most of them are in the cold neutral medium phase. In addition, we determined that the high-mass end of the Himass function is fitted well with a power-law function with an index of 2.3. Although two sequences of self-gravitating and diffuse clouds are expected to appear in theMtot–diagram according to previous works based on a plane-parallel model, the observational data show only a single sequence with large scattering within these two sequences. This implies that most of the clouds are mixtures of these two types of clouds. Moreover, we suggest the following scenario of molecular-gas formation: an Hi-dominant cloud evolved with increasing H2mass along a path ofby collecting diffuse gas before reaching and moving along the curves of the two sequences.