arXiv 1403.35312014-03-14astro-ph.GA

HCO、c-C3H和CF +：弥散、半透明和“旋臂”云中的三种新分子

HCO, c-C3H and CF+ : three new molecules in diffuse, translucent and "spiral-arm'' clouds

H. Liszt, J. Pety, M. Gerin, R. Lucas

备注：: A\%A in press
DOI：: 10.1051/0004-6361/201323320

摘要：

我们在IRAM 30米处使用EMIR接收器和FTS光谱仪，以195 kHz的光谱分辨率（$\approx$ 0.6 \kms）构造朝向明亮的河外背景源的吸收光谱。我们利用IRAM Plateau de Bure干涉仪合成了\hthcop和HCO在银河系HII区W 49的吸收光谱。%结果{HCO、\cc 3 h\和CF \p \在\EBV = 0.32和1.65 MAg的耀变体\bll \和3C 111中被探测到。HCO在掩星W 49的银道面“螺旋臂”云的吸收中被观测到。在\EBV \ = 0.32 mag（\AV \ = 1 mag）和$δ_τ$ / \EBV \ $\approx\ 0.003$ mag $^{-1}$的均方根噪声水平$δ_τ\approx 0.002$下，现在可以完全确定漫射/半透明气体的85 - 110 GHz吸收光谱中可检测分子种类的补充。} %结论{与OH、\hcop \和\cch一样，\cc 3 h\的相对丰度在扩散和致密分子气体之间变化很小，N（\cc 3 h）/N（{ \it o-c}- \c 3 h 2）$\approx$ 0.1。我们发现N（CF \p）/N（H $^{13}$ CO \p）$\approx 5$，N（CF \p）/N（\cch）$\approx$ 0.005-0.01，因为N（CF \p）随\EBV增加而增加，并且随着其他分子的柱密度，我们推断氟作为HF保留在气相中，远远超过\AV = 1 mag。（H $^{13}$ CO \p）= 16，朝向\bll，3C 111和朝向W 49的40 km/s旋臂云，这意味着X（HCO）$\approx 10^{-9}$，大约比暗云高10倍。HCO的行为与以前的建议一致，即它是由C \p \和\HH形成的，即使\AV \远高于1 MAG。（\hhco）/N（\HH CS）$>$ 32朝向3C 111，相比之下，7朝向TMC-1，证实了气相形成路线至\hhco的可能性。

英文摘要：

%methods {We used the EMIR receiver and FTS spectrometer at the IRAM 30m to construct absorption spectra toward bright extra-galactic background sources at 195 kHz spectral resolution ($\approx$ 0.6 \kms). We used the IRAM Plateau de Bure interferometer to synthesize absorption spectra of \hthcop\ and HCO toward the galactic HII region W49.} %results {HCO, \cc3h\ and CF\p\ were detected toward the blazars \bll\ and 3C111 having \EBV\ = 0.32 and 1.65 mag. HCO was observed in absorption from ``spiral-arm'' clouds in the galactic plane occulting W49. The complement of detectable molecular species in the 85 - 110 GHz absorption spectrum of diffuse/translucent gas is now fully determined at rms noise level $δ_τ\approx 0.002$ at \EBV\ = 0.32 mag (\AV\ = 1 mag) and $δ_τ$/\EBV\ $\approx\ 0.003$ mag$^{-1}$ overall.} %conclusions {As with OH, \hcop\ and \cch, the relative abundance of \cc3h\ varies little between diffuse and dense molecular gas, with N(\cc3h)/N({\it o-c}-\c3h2) $\approx$ 0.1. We find N(CF\p)/N(H$^{13}$CO\p) $\approx 5$, N(CF\p)/N(\cch) $\approx$ 0.005-0.01 and because N(CF\p) increases with \EBV\ and with the column densities of other molecules we infer that fluorine remains in the gas phase as HF well beyond \AV\ = 1 mag. We find N(HCO)/N(H$^{13}$CO\p) = 16 toward \bll, 3C111 and the 40 km/s spiral arm cloud toward W49, implying X(HCO) $\approx 10^{-9}$, about 10 times higher than in dark clouds. The behaviour of HCO is consistent with previous suggestions that it forms from C\p\ and \HH, even when \AV\ is well above 1 mag. The survey can be used to place useful upper limits on some species, for instance N(\hhco)/N(\HH CS) $>$ 32 toward 3C111, compared to 7 toward TMC-1, confirming the possibility of a gas phase formation route to \hhco.}

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