Multiwavelength observations of cirrus clouds in the North Celestial Loop: a study of the OH emission
Multiwavelength observations of cirrus clouds in the North Celestial Loop: a study of the OH emission
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DOI：
10.1111/j.1365-2966.2010.17105.x
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发表时间：
2010-10-01
影响因子：
4.8
通讯作者：
Martin, P. G.
中科院分区：
文献类型：
--
作者：
Barriault, L.;Joncas, G.;Martin, P. G.
新的1665和1667兆赫的OH观测是用绿岸望远镜在银河系高纬度的两个弥漫气体云的108个位置上以7角分的角分辨率进行的。追踪所有气体的IRAS 100 μ m红外强度与OH柱密度之间观察到线性相关，表明OH的数量随着视觉消光超过阈值A(V)近似为0.5而增加。N（OH）随N(H)单调增加，直至N（OH）近似于0.25-0.3 × 1014 cm-2。在较大的N（OH）值下，H (i)柱密度在N（H i）接近5 × 1020 cm-2时达到饱和，表明存在未被H i追踪的分子气体。在12CO积分强度和OH柱密度之间没有发现相关性，表明在这些扩散区域，OH可能比CO更好地追踪H-2。OH的形成需要至少接近2.2-2.9 x 1020 cm-2的H柱密度，但在云对星际辐射场屏蔽较少的区域，该值上升到N(H i) = 3.3 x 1020 cm-2。
New 1665- and 1667-MHz OH observations were made with the Green Bank Telescope at an angular resolution of 7 arcmin of 108 locations over two diffuse gas clouds at high Galactic latitude. A linear correlation is observed between the IRAS 100 mu m infrared intensity, which traces all the gas, and the OH column density, indicating that the amount of OH increases with the visual extinction above a threshold value of A(V) approximate to 0.5. N(OH) increases monotonically with N(H i) in up to N(OH) approximate to 0.25-0.3 x 1014 cm-2. At greater values of N(OH) the H i column density saturates at N(H i) approximate to 5 x 1020 cm-2, suggesting that there is molecular gas not traced by H i. No correlation is found between the 12CO integrated intensity and the OH column density, indicating that OH might be a better tracer of H-2 than CO in those diffuse regions. An H i column density of at least approximate to 2.2-2.9 x 1020 cm-2 is needed for the formation of OH, but in regions where the cloud is less shielded from the interstellar radiation field the value rises to N(H i) = 3.3 x 1020 cm-2.