论文标题
OH分子云中的进化
OH Evolution in Molecular Clouds
论文作者
论文摘要
在各种环境中，我们对141个分子云进行了OH 18厘米的调查，其中包括33个光学乌云，98个Planck银河冷团（PGCC）和10个带有Arecibo望远镜的Spitzer暗云。局部热平衡的偏差对于OH主线和卫星线的强度比很常见。当$ A \ rm_v $小于3 mag时，发现OH 1667 MHz的线强度与视觉灭绝$ a \ rm_v $线性相关。它通过采用源自具有一个Sigma不确定性的蒙特卡洛模拟的激发温度来转换为OH柱密度。相对于h $ _2 $和$ a \ rm_v $，oh丰度$ x $（oh）之间的关系遵循经验公式， \ begin {qore} \ nonumber \ frac {x（\ textrm {oh}）}} {10^{ - 7}} = 1.3^{+0.4} _ { - 0.4}+6.3}+6.3^^{+0.5} \ textrm {exp}（ - \ frac {a_ \ textrm {v}}} {2.9^{+0.6} _ { - 0.6}}）。 \ end {方程}在OH和$^{13} $ CO强度之间发现线性相关。此外，OH和$^{13} $ co的非热速度分散与密切相关。这些结果意味着OH和$^{13} $ co之间的化学演变和空间占用。 OH和HI狭窄的自我吸收（HINSA）之间的色谱柱密度与非热速度分散之间没有明显的相关性，表明OH和HINSA之间的化学进化和空间体积占用不同。使用HINSA分析的年龄信息，发现OH丰度$ x $（OH）与云年龄相线性增加，这与以前的模拟一致。检测到没有相应CO发射的14个OH组件，这意味着OH在追踪“涂层”分子气体中的有效性。
We have conducted OH 18 cm survey toward 141 molecular clouds in various environments, including 33 optical dark clouds, 98 Planck Galactic cold clumps (PGCCs) and 10 Spitzer dark clouds with the Arecibo telescope. The deviations from local thermal equilibrium are common for intensity ratios of both OH main lines and satellite lines. Line intensity of OH 1667 MHz is found to correlate linearly with visual extinction $A\rm_V$ when $A\rm_V$ is less than 3 mag. It was converted into OH column density by adopting excitation temperature derived from Monte Carlo simulations with one sigma uncertainty. The relationship between OH abundance $X$(OH) relative to H$_2$ and $A\rm_V$ is found to follow an empirical formula, \begin{equation} \nonumber \frac{X(\textrm{OH})}{10^{-7}} = 1.3^{+0.4}_{-0.4} + 6.3^{+0.5}_{-0.5}\times \textrm{exp}(-\frac{A_\textrm{V}}{2.9^{+0.6}_{-0.6}}). \end{equation} Linear correlation is found between OH and $^{13}$CO intensity. Besides, nonthermal velocity dispersions of OH and $^{13}$CO are closely correlated. These results imply tight chemical evolution and spatial occupation between OH and $^{13}$CO. No obvious correlation is found between column density and nonthermal velocity dispersion of OH and HI Narrow Self-Absorption (HINSA), indicating different chemical evolution and spatial volume occupation between OH and HINSA. Using the age information of HINSA analysis, OH abundance $X$(OH) is found to increase linearly with cloud age, which is consistent with previous simulations. Fourteen OH components without corresponding CO emission were detected, implying the effectiveness of OH in tracing the `CO-dark' molecular gas.
