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arXiv 0812.0558astro-ph
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银河核球的丰度：来自行星状星云和巨星的结果

Abundances in the Galactic bulge: results from planetary nebulae and giant stars

C. Chiappini, S. Gorny, G. Stasinska, B. Barbuy

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23 pages, 15 figures, 16 pages of online material, A&A in press
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摘要：

我们对银河系核球化学演化的理解需要测定巨星和行星状星云（PNE）大样本的丰度。我们讨论PNE丰度在银河系的隆起，并比较这些结果与文献中提出的巨星。我们提出了最大的，高质量的数据集，可用于PNE在银河系的凸起方向（内盘/凸起）。为了比较的目的，我们还考虑了一个样本的PNE在大麦云（LMC）。我们以一致的方式推导出所研究的所有Pne的元素丰度。通过比较丰度的凸起，内盘，和LMC，我们确定的PN祖细胞的演变过程中没有被修改的元素，可以用来跟踪凸起的化学富集的历史。然后，我们比较了PN丰度与隆起场巨星的丰度。在核球的金属丰度，我们发现，O和Ne的丰度接近的值为星际介质在PN祖形成的时间，因此这些元素可以被用来作为示踪剂的核球化学演化，以同样的方式作为S和Ar，预计不会受到核合成过程中的PN祖的演变。PN氧丰度分布向低值移动了0.3 dex，相对于巨星给出的分布。Ne和S也出现类似的变化。我们讨论了可能的原因，这种PNE巨星的差异，并得出结论，这可能是由于系统误差的丰度推导中的巨人或PNE（或两者）。我们对在化学演化研究中使用绝对丰度提出重要警告。

英文摘要：

Our understanding of the chemical evolution of the Galactic bulge requires the determination of abundances in large samples of giant stars and planetary nebulae (PNe). We discuss PNe abundances in the Galactic bulge and compare these results with those presented in the literature for giant stars. We present the largest, high-quality data-set available for PNe in the direction of the Galactic bulge (inner-disk/bulge). For comparison purposes, we also consider a sample of PNe in the Large Magellanic Cloud (LMC). We derive the element abundances in a consistent way for all the PNe studied. By comparing the abundances for the bulge, inner-disk, and LMC, we identify elements that have not been modified during the evolution of the PN progenitor and can be used to trace the bulge chemical enrichment history. We then compare the PN abundances with abundances of bulge field giant. At the metallicity of the bulge, we find that the abundances of O and Ne are close to the values for the interstellar medium at the time of the PN progenitor formation, and hence these elements can be used as tracers of the bulge chemical evolution, in the same way as S and Ar, which are not expected to be affected by nucleosynthetic processes during the evolution of the PN progenitors. The PN oxygen abundance distribution is shifted to lower values by 0.3 dex with respect to the distribution given by giants. A similar shift appears to occur for Ne and S. We discuss possible reasons for this PNe-giant discrepancy and conclude that this is probably due to systematic errors in the abundance derivations in either giants or PNe (or both). We issue an important warning concerning the use of absolute abundances in chemical evolution studies.

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