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arXiv 1702.03039astro-ph.GAastro-ph.SR
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大样本行星状星云中C II $λ$ 6578准谱线的动力学

The Kinematics of the Permitted C II $λ$ 6578 Line in a Large Sample of Planetary Nebulae

Michael G. Richer, Genaro Suárez, José Alberto López, María Teresa García Díaz

摘要:

本文介绍了76个行星状星云中83条视线的C II $λ$ 6578允许谱线的高光谱分辨率光谱观测结果,其中大部分是用位于Sierra San Pedro Mártir的国家天文台的2.1m望远镜上的Manchester Echelle摄谱仪获得的。我们研究了C Ⅱ $λ$ 6578允许谱线相对于其它允许谱线和碰撞激发谱线的运动学。统计上,我们发现,运动学的C II $λ$ 6578线是不是那些预期的,如果这条线产生的重组的C $^{2+}$离子或荧光的C $^+$离子在电离平衡中的化学均匀的星云等离子体,但相反,它的运动学是那些适合的体积比预期的更内部。这个样本中的行星状星云具有明确的形态,并且与银河系凸起中的对应物相比,H $α$线宽限制在有限的范围内(没有大的值),这两者都可以解释为年轻星云壳的结果,星云模型也支持这一推论。关于长期存在的化学丰度之间的差异推断允许和碰撞激发的发射线在光电离星云,我们的研究结果意味着,多个等离子体成分通常发生在行星状星云。

英文摘要:

We present spectroscopic observations of the C II $λ$6578 permitted line for 83 lines of sight in 76 planetary nebulae at high spectral resolution, most of them obtained with the Manchester Echelle Spectrograph on the 2.1\,m telescope at the Observatorio Astronómico Nacional on the Sierra San Pedro Mártir. We study the kinematics of the C II $λ$6578 permitted line with respect to other permitted and collisionally-excited lines. Statistically, we find that the kinematics of the C II $λ$6578 line are not those expected if this line arises from the recombination of C$^{2+}$ ions or the fluorescence of C$^+$ ions in ionization equilibrium in a chemically-homogeneous nebular plasma, but instead its kinematics are those appropriate for a volume more internal than expected. The planetary nebulae in this sample have well-defined morphology and are restricted to a limited range in H$α$ line widths (no large values) compared to their counterparts in the Milky Way bulge, both of which could be interpreted as the result of young nebular shells, an inference that is also supported by nebular modeling. Concerning the long-standing discrepancy between chemical abundances inferred from permitted and collisionally-excited emission lines in photoionized nebulae, our results imply that multiple plasma components occur commonly in planetary nebulae.

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