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arXiv 1007.0005astro-ph.GA
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WIM的H-α和自由-自由发射

H-alpha and Free-Free Emission from the WIM

Ruobing Dong, B. T. Draine

摘要:

最近的观测发现,在弥漫电离ISM(所谓的WIM)中,H-α与自由-自由射电连续谱的比率惊人地高,对应的电子温度仅为~ 3000 K。这种低温在被认为是光电离的气体中是出乎意料的。我们考虑一个三分量模型的观察到的漫发射,由(1)光电离气体,(2)气体,是重组和冷却,(3)冷氢气体的混合。该模型可以成功地再现所观察到的强度的自由-自由连续,H-α,碰撞激发线,如NII 6583。如Wood和Reynolds(1999年)所建议的那样,为了重现游离-游离到H-α的低观测值,光电离区域的PAH丰度必须降低约3倍,并且约20%的扩散H-α必须从尘埃颗粒反射。

英文摘要:

Recent observations have found the ratio of H-alpha to free-free radio continuum to be surprisingly high in the diffuse ionized ISM (the so-called WIM), corresponding to an electron temperature of only ~3000K. Such low temperatures were unexpected in gas that was presumed to be photoionized. We consider a 3-component model for the observed diffuse emission, consisting of a mix of (1) photoionized gas, (2) gas that is recombining and cooling, and (3) cool H I gas. This model can successfully reproduce the observed intensities of free-free continuum, H-alpha, and collisionally-excited lines such as NII 6583. To reproduce the low observed value of free-free to H-alpha, the PAH abundance in the photoionized regions must be lowered by a factor ~3, and ~20% of the diffuse H-alpha must be reflected from dust grains, as suggested by Wood & Reynolds (1999).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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