论文标题
海马吞咽了什么？ Apex 170 GHz观察海马红外乌云的化学条件
What did the seahorse swallow? APEX 170 GHz observations of the chemical conditions in the Seahorse infrared dark cloud
论文作者
论文摘要
我们使用Apex望远镜观察沿丝状海马红外乌云的全部范围，以约170 GHz的频率朝着14个位置出现的光谱线。总共检测到六个光谱线过渡（$ \geq3σ$），也就是说，$（n_j = 4_4-3_3）$，h $^{13} $ cn $（j = 2-1）$，h $^{13} $^{13} $ co $^+（j = 2-1）和c $ _2 $ h $（n = 2-1）$。虽然在每个来源中都检测到H $^{13} $ co $^+$，并且Hn $^{13} $ C在每个来源中都检测到，C $ _2 $ H和H $^{13} $ CN的检测率分别为92.9％和85.7％。只有一个源（SMM 3）显示可检测到的SIO发射（检测率为7.1％）。三个集团（SMM 5、6和7）显示了SO，H $^{13} $ CN，H $^{13} $ co $^+$，Hn $^{13} $ C，以及C $ _2 $ _2 $ h hn in papsorption。我们发现了派生的分子丰度之间的三个正相关，其中c $ _2 $ h和hn $^{13} $ c和hn $^{13} $ c和h $ c和h $^{13} $ co $^+$是最重要的（相关系数$ r \ simeq0.9 $）。我们发现的统计上最重要的进化趋势是c $ _2 $ _2 $ h的丰度下降，以及$ [{\ rm hn^{13} c}]/[{{\ rm h^{13} cn} cn} $比率，因为团块从黑暗的舞台上从黑暗的舞台上转变为ir Bright Bright Stape and the Ir Bright Stape and the Hii Hii Hii and to Hii Hii。我们发现不同分子丰度之间的相关性可以理解为来自气相电子（电离程度）和原子碳的丰度产生的相关性。我们发现的[C $ _2 $ H]进化指标与以前的研究一致，可以通过C $ _2 $ h向其他物种的转换（例如CO）进行解释，当时团块温度升高时，尤其是在集块中热分子核心点火后。 $ [{\ rm hn^{13} c}]/[{\ rm h^{13} cn}] $的降低，因为团块的发展也可能反映出团块温度的升高，这会导致HCN的增强形成HCN及其$^{13} $ C ISOPOPOLOGUE。
We used the APEX telescope to observe spectral lines occurring at about 170 GHz frequency towards 14 positions along the full extent of the filamentary Seahorse infrared dark cloud. Six spectral line transitions were detected ($\geq3σ$) altogether, namely, SO$(N_J=4_4-3_3)$, H$^{13}$CN$(J=2-1)$, H$^{13}$CO$^+(J=2-1)$, SiO$(J=4-3)$, HN$^{13}$C$(J=2-1)$, and C$_2$H$(N=2-1)$. While SO, H$^{13}$CO$^+$, and HN$^{13}$C were detected in every source, the detection rates for C$_2$H and H$^{13}$CN were 92.9% and 85.7%, respectively. Only one source (SMM 3) showed detectable SiO emission (7.1% detection rate). Three clumps (SMM 5, 6, and 7) showed the SO, H$^{13}$CN, H$^{13}$CO$^+$, HN$^{13}$C, and C$_2$H lines in absorption. We found three positive correlations among the derived molecular abundances, of which those between C$_2$H and HN$^{13}$C and HN$^{13}$C and H$^{13}$CO$^+$ are the most significant (correlation coefficient $r\simeq0.9$). The statistically most significant evolutionary trends we uncovered are the drops in the C$_2$H abundance and in the $[{\rm HN^{13}C}]/[{\rm H^{13}CN}]$ ratio as the clump evolves from an IR dark stage to an IR bright stage and then to an HII region. The correlations we found between the different molecular abundances can be understood as arising from the gas-phase electron (ionisation degree) and atomic carbon abundances. The [C$_2$H] evolutionary indicator we found is in agreement with previous studies, and can be explained by the conversion of C$_2$H to other species (e.g. CO) when the clump temperature rises, especially after the ignition of a hot molecular core in the clump. The decrease of $[{\rm HN^{13}C}]/[{\rm H^{13}CN}]$ as the clump evolves is also likely to reflect the increase in the clump temperature, which leads to an enhanced formation of HCN and its $^{13}$C isotopologue.
