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arXiv 2308.04577astro-ph.GA
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行星状星云中的低电离结构——III. 物理化学参数与激发机制的统计分析

Low-ionization structures in planetary nebulae -- III. The statistical analysis of physico-chemical parameters and excitation mechanisms

M. Belén Mari, Stavros Akras, Denise R. Gonçalves

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17 pages, 10 figures
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AI总结：

本文基于迄今最大样本，统计对比行星状星云中低电离结构与高电离结构的物理化学参数及激发机制，发现激波并非大多数低电离结构的主要激发来源。

摘要：

在首次对行星状星云（PNe）中的低电离结构（LISs）进行详细研究近30年后，我们通过收集文献中已发表的数据，对其物理、化学和激发性质进行了统计分析。该分析通过对比大样本PNe中低电离结构与高电离结构（边缘或壳层）之间的差异来进行，以突出这些结构之间的显著区别。我们的动机是基于迄今收集到的最大LISs样本得出稳健的结果。（i）确实，LISs的电子密度（N$_{e}$[S~II]）低于边缘/壳层。（ii）两组的氮电子温度（T$_{e}$[N~II]）相似，而基于边缘/壳层[O~III]的T$_{e}$则呈现双峰分布，尽管高电离和低电离结构的T$_{e}$[O~III]中值相近。（iii）两组之间He、N、O、Ne、Ar、Cl和S的总丰度未观察到显著变化。（iv）通过对多个诊断图的分析，LISs在激发方面与边缘/壳层区分开来。基于两个大型光致电离模型和激波模型网格，我们表明两种机制之间存在重要重叠，尤其是在涉及低电离线比时。我们发现了一个良好的高速激波示踪剂，以及一个依赖于温度敏感线比的高速和低速激波指示剂。总之，两种激发机制都可能存在，但激波不可能是大多数PNe中LISs的主要激发来源。

英文摘要：

Nearly 30 years after the first detailed studies of low-ionization structures (LISs) in planetary nebulae (PNe), we perform a statistical analysis of their physical, chemical and excitation properties, by collecting published data in the literature. The analysis was made through the contrast between LISs and high-ionization structures -- rims or shells -- for a large sample of PNe, in order to highlight significant differences between these structures. Our motivation was to find robust results based on the largest sample of LISs gathered so far. (i) Indeed, LISs have lower electron densities (N$_{e}$[S~II]) than the rims/shells. (ii) The nitrogen electron temperatures (T$_{e}$[N~II]) are similar between the two groups, while a bimodal distribution is observed for the T$_{e}$ based on [O~III] of the rims/shells, although the high- and low-ionization structures have T$_{e}$[O~III] of similar median values. (iii) No significant variations are observed in total abundances of He, N, O, Ne, Ar, Cl and S between the two groups. (iv) Through the analysis of several diagnostic diagrams, LISs are separated from rims/shells in terms of excitation. From two large grids of photoionization and shock models, we show that there is an important overlap between both mechanisms, particularly when low-ionization line-ratios are concerned. We found a good tracer of high-velocity shocks, as well as an indicator of high- and low-velocity shocks that depends on temperature-sensitive line ratios. In conclusion, both excitation mechanisms could be present, however shocks cannot be the main source of excitation for most of the LISs of PNe.

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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