凤凰矮星系中发现的第一个行星状星云的VLT/FORS1分光光度法
VLT/FORS1 spectrophotometry of the first planetary nebula discovered in the Phoenix dwarf galaxy
摘要：
背景：在对本星系群矮星系凤凰进行FORS成像时，发现了一个行星状星云（PN）候选者。目的：使用这个PN来补充红巨星的丰度。方法：应用FORS光谱对PN进行分型。经验的方法和光电离建模被用来获得元素丰度的发射线通量和中央恒星的特点。结果如下：对于被认为是测量形成PN的星际介质金属丰度最可靠的元素，[O/H] ~-0. 46和[Ar/H] ~-1. 03。[O/H]的测量误差较低，但由于PN前体恒星中的富氧问题尚未解决，因此具有更大的不确定性。结论：早于2 Gyr ago（中心恒星年龄的下限），ISM的Z = 0.002- 0.008，比恒星提供的范围稍微更富金属。比较我们的PN到恒星的值与其他矮本星系群星系的调查，凤凰似乎是一个离群值。
英文摘要：
Context: A planetary nebula (PN) candidate was discovered during FORS imaging of the Local Group dwarf galaxy Phoenix. Aims: Use this PN to complement abundances from red-giant stars. Methods: FORS spectroscopy was used to confirm the PN classification. Empirical methods and photoionization modeling were used to derive elemental abundances from the emission line fluxes and to characterize the central star. Results: For the elements deemed most reliable for measuring the metallicity of the interstellar medium (ISM) from which the PN formed, [O/H] ~ -0.46 and [Ar/H] ~ -1.03. [O/H] has lower measurement errors but greater uncertainties due to the unresolved issue of oxygen enrichment in the PN precursor star. Conclusions: Earlier than 2 Gyr ago (the lower limit of the derived age for the central star) the ISM had Z = 0.002--0.008, a range slightly more metal-rich than the one provided by stars. Comparing our PN-to-stellar values to surveys for other dwarf Local Group galaxies, Phoenix appears as an outlier.
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