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bHROS high spectral resolution observations of PN forbidden and recombination line profiles

机译:PN禁止和重组谱线的bHROS高光谱分辨率观察

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摘要

We have acquired high spectral resolution observations (R=150,000) of the planetary nebulae NGC 7009 and NGC 6153, using bHROS on Gemini South. Observations of this type may provide a key to understanding why optical recombination lines (ORLs) yield systematically higher heavy element abundances for photoionized nebulae than do the classical forbidden collisionally excited lines (CELs) emitted by the same ions; NGC 7009 and NGC 6153 have notably high ORL/CEL abundance discrepancy factors (ADFs) of 5 and 10, respectively. Due to the opposite temperature dependences of ORLs and CELs, ORLs should be preferentially emitted by colder plasma. Our bHROS observations of NGC 7009 reveal that the [O III] 4363A CEL has a FWHM linewidth that is 1.5 times larger than that shown by O II ORLs in the same spectrum, despite the fact that all of these lines are emitted by the O2+ ion. The bHROS spectra of NGC 6153 also show that its O II ORLs have significantly narrower linewidths than do the [O III] 4363A and 5007A lines but, in addition, the [O III] 4363A and 5007A lines show very different velocity profiles, implying the presence of large temperature variations in the nebula.
机译:我们已经使用双子座南的bHROS获得了行星状星云NGC 7009和NGC 6153的高光谱分辨率观测值(R = 150,000)。这种类型的观察结果可能是理解为什么光重组线(ORL)会比同一个离子发射的经典的禁止碰撞激发线(CEL)产生系统更高的重离子丰度的关键。 NGC 7009和NGC 6153分别具有5和10的高ORL / CEL丰度差异因子(ADF)。由于ORL和CEL的温度依赖性相反,因此ORL应优先由较冷的等离子体发射。我们对NGC 7009的bHROS观察表明,[O III] 4363A CEL的FWHM线宽是同一光谱中O II ORL显示的FWHM线宽的1.5倍,尽管事实上所有这些线都是由O2 +离子发射的。 NGC 6153的bHROS谱还表明,与[O III] 4363A和5007A谱线相比,其O II ORL的线宽明显更窄,但是[O III] 4363A和5007A谱线显示出非常不同的速度分布,这意味着星云中存在较大的温度变化。

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