IC 418中荧光和复合对发射线的激发
Excitation of emission lines by fluorescence and recombination in IC 418
摘要：
我们预测的CII，NI，NII，OI和OII线的强度，并将它们与IC 418的深光谱调查进行比较，以测试星光的连续荧光对星云发射线的激发效果。我们的计算使用星云模型和其中心恒星的合成光谱，考虑到连续荧光和重组线的激发。由于星云的低激发条件，NII光谱主要由荧光产生，但许多CII和OII线的荧光激发多于复合。在中性包线中，NI允许谱线由荧光激发，而OI谱线几乎全部由复合激发。电子激发产生OI的禁戒线，而连续荧光激发大部分NI的禁戒线强度。因此，低于莱曼极限的荧光激发的谱线提出了一种新的诊断方法来探索星云的光解区域。
英文摘要：
We predict intensities of lines of CII, NI, NII, OI and OII and compare them with a deep spectroscopic survey of IC 418 to test the effect of excitation of nebular emission lines by continuum fluorescence of starlight. Our calculations use a nebular model and a synthetic spectrum of its central star to take into account excitation of the lines by continuum fluorescence and recombination. The NII spectrum is mostly produced by fluorescence due to the low excitation conditions of the nebula, but many CII and OII lines have more excitation by fluorescence than recombination. In the neutral envelope, the NI permitted lines are excited by fluorescence, and almost all the OI lines are excited by recombination. Electron excitation produces the forbidden optical lines of OI, but continuum fluorescence excites most of the NI forbidden line intensities. Lines excited by fluorescence of light below the Lyman limit thus suggest a new diagnostic to explore the photodissociation region of a nebula.
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