论文标题
[CI]（$^3p_1 $ - $^3p_0 $）对大型恒星形成区域RCW38的排放：进一步的证据证明分子气体密度分布，
Observations of the [CI] ($^3P_1$-$^3P_0$) emission toward the massive star-forming region RCW38: further evidence for highly-clumped density distribution of the molecular gas
论文作者
论文摘要
我们使用ASTE 10 m sub-mm望远镜RCW38（以银河系中最年轻的超级明星群rcw38）使用ASTE 10 m sub-mm望远镜的$^3p_1 $ - $^3p_0 $ fine Atomic Carbon。将检测到的[CI]发射与Fukui等人中介绍的CO $ J $ = 1-0图像立方体进行了比较。 （2016）的角度分辨率为40 $^{\ prime \ prime} $（$ \ sim $ 0.33 PC）。该集群中[CI]排放的总体分布类似于$^{13} $ CO排放。发现[CI]发射的光学深度为$τ$ = 0.1-0.6，这主要是光学上薄的发射。从[CI]集成强度到H $ _2 $列密度的经验转换因子估计为$ x _ {\ rm [ci]} $ = 6.3 $ = 6.3 $ \ times $ 10 $ 10 $^{20} $ cm $^{ - 2} $ k $ k $ k $ k $ k $ k $ km $ km $ km $ km $ km $^$ a $ a $ a $ a $ a $ a $ a $ a $ a $ a $ a $ a $ 10} mag）和1.4 $ \ times $ 10 $^{21} $ cm $^{ - 2} $ k $^{ - 1} $ km $ $^{ - 1} $ s（对于$ a_v $ 10-100 mag）。 [CI]与CO（$ n _ {\ rm [CI]}/n _ {\ rm co} $）的列密度比定为$ \ sim $ 0.1，对于$ \ sim $ 0.1，对于$ a_v $ of 10-100 mag，这与Ikeda等人的Orion Cloud相符。 （2002）。但是，我们的结果涵盖了高达100 mag的$ A_V $制度，这比Orion中的覆盖范围宽，最高可达$ \ sim $ 60 mag。在高$ a_v $区域中，很难用平行平行的光解离区（PDR）模型来解释如此高的[CI]/CO比率，该模型预测，由于紫外线（UV）辐射的重屏蔽，该比率接近0。我们的结果表明，该集群中的分子气体是高度块状的，即使在平均$ A_V $值为100 mag的$ A_V $值下，也可以深入紫外线辐射。最近的理论作品提出了与此类集成气体分布相一致的模型，该模型具有亚-PC团块的大小（例如Tachihara等人，2018年）。
We present observations of the $^3P_1$-$^3P_0$ fine-structure line of atomic carbon using the ASTE 10 m sub-mm telescope towards RCW38, the youngest super star cluster in the Milky Way. The detected [CI] emission is compared with the CO $J$ = 1-0 image cube presented in Fukui et al. (2016) which has an angular resolution of 40$^{\prime \prime}$ ($\sim$ 0.33 pc). The overall distribution of the [CI] emission in this cluster is similar to that of the $^{13}$CO emission. The optical depth of the [CI] emission was found to be $τ$ = 0.1-0.6, suggesting mostly optically thin emission. An empirical conversion factor from the [CI] integrated intensity to the H$_2$ column density was estimated as $X_{\rm [CI]}$ = 6.3 $\times$ 10$^{20}$ cm$^{-2}$ K$^{-1}$ km$^{-1}$ s (for visual extinction: $A_V$ $\le$ 10 mag) and 1.4 $\times$ 10$^{21}$ cm$^{-2}$ K$^{-1}$ km$^{-1}$ s (for $A_V$ of 10-100 mag). The column density ratio of the [CI] to CO ($N_{\rm [CI]}/N_{\rm CO}$) was derived as $\sim$ 0.1 for $A_V$ of 10-100 mag, which is consistent with that of the Orion cloud presented in Ikeda et al. (2002). However, our results cover an $A_V$ regime of up to 100 mag, which is wider than the coverage found in Orion, which reach up to $\sim$ 60 mag. Such a high [CI]/CO ratio in a high $A_V$ region is difficult to be explained by the plane-parallel photodissociation region (PDR) model, which predicts that this ratio is close to 0 due to the heavy shielding of the ultraviolet (UV) radiation. Our results suggest that the molecular gas in this cluster is highly clumpy, allowing deep penetration of UV radiation even at averaged $A_V$ values of 100 mag. Recent theoretical works have presented models consistent with such clumped gas distribution with a sub-pc clump size (e.g., Tachihara et al. 2018).
