We present an analysis of elemental abundances of He, N, O, Ne, S, and Ar in Magellanic Cloud planetary nebulae (PNe) and focus initially on 14 PNe in the Small Magellanic Cloud (SMC). We derive the abundances from a combination of deep, high-dispersion optical spectra, as well as mid-infrared (IR) spectra from the Spitzer Space Telescope. A detailed comparison with prior SMC PN studies shows that significant variations in relative emission-line flux determinations among the authors, lead to systematic discrepancies in derived elemental abundances between studies that are 0.15 dex, in spite of similar analysis methods. We use ionic abundances derived from IR emission lines, including those from ionization stages not observable in the optical, to examine the accuracy of some commonly used recipes for ionization correction factors (ICFs). These ICFs, which were developed for ions observed in the optical and ultraviolet, relate ionic abundances to total elemental abundances. We find that most of these ICFs work very well even in the limit of substantially sub-solar metallicities, except for PNe with very high ionization. Our abundance analysis shows enhancements of He and N that are predicted from prior dredge-up processes of the progenitors on the asymptotic giant branch (AGB), as well as the well-known correlations among O, Ne, S, and Ar that are little affected by nucleosynthesis in this mass range. We identify MG 8 as an interesting limiting case of a PN central star with a ≈3.5 M ☉ progenitor in which hot-bottom burning did not occur in its prior AGB evolution. We find no evidence for O depletion in the progenitor AGB stars via the O-N cycle, which is consistent with predictions for lower-mass stars. We also find low S/O ratios relative to SMC H II regions, with a deficit comparable to what has been found for Galactic PNe. Finally, the elemental abundances of one object, SMP-SMC 11, are more typical of SMC H II regions, which raises some doubt about its classification as a PN.
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机译：我们目前对麦哲伦星系行星星云（PNe）中He，N，O，Ne，S和Ar的元素丰度进行分析，并首先关注小麦哲伦星系（SMC）中的14 PNe。我们从深，高色散光谱以及Spitzer空间望远镜的中红外（IR）光谱中组合得出丰度。与以前的SMC PN研究进行的详细比较表明，尽管有相似的分析方法，但作者之间相对发射谱线通量的确定存在显着差异，导致研究之间的衍生元素丰度存在系统差异，为0.15 dex。我们使用源自红外发射谱线的离子丰度，包括来自光学中无法观察到的离子化阶段的离子丰度，来检查一些常用的电离校正因子（ICF）配方的准确性。这些ICF是为在光学和紫外线中观察到的离子而开发的，将离子丰度与总元素丰度相关联。我们发现，除了具有非常高电离的PNe之外，大多数这些ICF甚至在基本上亚太阳能金属的极限下也能很好地工作。我们的丰度分析显示，从渐近巨分支（AGB）上的祖细胞的先前挖泥过程预测，He和N的增强，以及O，Ne，S和Ar之间的众所周知的相关性很小在这个质量范围内受到核合成的影响。我们将MG 8识别为PN中心星的有趣的极限情况，该中心星具有≈3.5M gen的祖先，在其先前的AGB演化过程中并未发生热底燃烧。我们没有发现通过O-N循环在祖先AGB恒星中消耗O的证据，这与对低质量恒星的预测是一致的。我们还发现相对于SMC H II地区而言，S / O比率较低，其缺陷与银河PNe的缺陷相当。最后，一个对象SMP-SMC 11的元素丰度在SMC H II区更为典型，这使人们对其分类为PN提出了一些疑问。
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