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arXiv 1210.7654astro-ph.GA
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原行星盘的辐射热化学模型。IV模拟Herbig Ae圆盘的CO振转辐射

Radiation thermo-chemical models of protoplanetary discs. IV Modelling CO ro-vibrational emission from Herbig Ae discs

Wing-Fai Thi, Inga Kamp, Peter Woitke, Gerrit van des Plas, Rosina Bertelsen, Laurent Wiesenfeld

备注：
22 pages, 27 figures, accepted for publication in A&A
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摘要：

赫比格Ae星和金牛T星周围的光盘的一氧化碳振转辐射与强紫外线辐射表明，荧光泵浦从地面X1西格玛+的电子A1 Pi状态的CO应考虑在光盘模型。我们实现了一个CO模型分子，包括多达50个旋转水平内的9个振动水平的地面和A激发态的辐射光化学代码ProDiMo。我们考虑了CO与氢分子、氢原子、氦和电子的碰撞。我们使用标准标度律估计了丢失碰撞率，并讨论了它们的局限性。UV荧光和IR泵浦对振转v > 1能级的布居的影响。v = 1的旋转能级在大约4.6微米的辐射温度和气体动力学温度之间的旋转温度下填充。紫外泵浦效率随着光盘质量的减小而增加。结果是，测量振动能级之间相对布居数的振动温度高于盘气体动力学温度（超热布居数）。旋转温度从基本的转变使用光学厚12CO线不反映气体动力学温度。LTE中存在能量低于1000 K的CO纯转动能级，但对模型中包含的许多振动能级敏感。12CO纯转动谱线在Eupper=2000 K的跃迁中具有很高的光学厚度。（节略）

英文摘要：

The carbon monoxide rovibrational emission from discs around Herbig Ae stars and T Tauri stars with strong ultraviolet emissions suggests that fluorescence pumping from the ground X1 Sigma+ to the electronic A1 Pi state of CO should be taken into account in disc models. We implemented a CO model molecule that includes up to 50 rotational levels within nine vibrational levels for the ground and A excited states in the radiative photochemical code ProDiMo. We took CO collisions with hydrogen molecules, hydrogen atoms, helium, and electrons into account. We estimated the missing collision rates using standard scaling laws and discussed their limitations. UV fluorescence and IR pumping impact on the population of ro-vibrational v > 1 levels. The v = 1 rotational levels are populated at rotational temperatures between the radiation temperature around 4.6 micron and the gas kinetic temperature. The UV pumping efficiency increases with decreasing disc mass. The consequence is that the vibrational temperatures, which measure the relative populations between the vibrational levels, are higher than the disc gas kinetic temperatures (suprathermal population). Rotational temperatures from fundamental transitions derived using optically thick 12CO lines do not reflect the gas kinetic temperature. CO pure rotational levels with energies lower than 1000 K are populated in LTE but are sensitive to a number of vibrational levels included in the model. The 12CO pure rotational lines are highly optically thick for transition from levels up to Eupper=2000 K. (abridged)

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