PHOTOCHEMISTRY IN THE INNER LAYERS OF CLUMPY CIRCUMSTELLAR ENVELOPES: FORMATION OF WATER IN C-RICH OBJECTS AND OF C-BEARING MOLECULES IN O-RICH OBJECTS
PHOTOCHEMISTRY IN THE INNER LAYERS OF CLUMPY CIRCUMSTELLAR ENVELOPES: FORMATION OF WATER IN C-RICH OBJECTS AND OF C-BEARING MOLECULES IN O-RICH OBJECTS
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块状星状包膜内层的光化学：富碳天体中水的形成和富氧天体中含碳分子的形成
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发表时间：
2010
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通讯作者：
M. Guélin
中科院分区：
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作者：
M. Agúndez;J. Cernicharo;M. Guélin
提出了一种基于星际紫外光子穿透渐进巨分支星周围块状星周包层（CSE）内层的机制来解释在此类物体中观察到的非平衡化学。我们通过一个简单的建模方法表明，在具有一定程度的块状或适度低质量损失率（几个10−7百万年-1）的CSE中，光化学可以发生在温暖而致密的内层，引起化学成分的重要变化。在富碳的物体中，水蒸气和氨的丰度相对于H2为10−8-10−6，而在富氧的包层中，氨和含碳分子（如HCN和CS）的丰度相对于H2为10−9-10−7。所提出的机制将解释赫歇尔空间天文台最近在富碳包层IRC+10216中观测到的暖水蒸气，并预测在其他富碳物体中应该可以检测到H2O。
A mechanism based on the penetration of interstellar ultraviolet photons into the inner layers of clumpy circumstellar envelopes (CSEs) around asymptotic giant branch stars is proposed to explain the non-equilibrium chemistry observed in such objects. We show through a simple modeling approach that in CSEs with a certain degree of clumpiness or with moderately low mass loss rates (a few 10−7 M☉ yr−1) a photochemistry can take place in the warm and dense inner layers, inducing important changes in the chemical composition. In carbon-rich objects water vapor and ammonia would be formed with abundances of 10−8–10−6 relative to H2, while in oxygen-rich envelopes ammonia and carbon-bearing molecules such as HCN and CS would form with abundances of 10−9–10−7 relative to H2. The proposed mechanism would explain the recent observation of warm water vapor in the carbon-rich envelope IRC+10216 with the Herschel Space Observatory and predict that H2O should be detectable in other carbon-rich objects.