十个银河系行星状星云与HST/STIS的共空间长缝紫外/光学光谱I.观测、全球发射线测量和CNO丰度的描述
Co-spatial Long-slit UV/Optical Spectra of Ten Galactic Planetary Nebulae with HST/STIS I. Description of the Observations, Global Emission-line Measurements, and CNO Abundances
摘要：
我们目前的观测和初步分析，从HST/STIS计划，以获得第一个共空间，紫外光光谱的10个银河系行星状星云（PNe）。我们的主要目标是在紫外光范围内以前所未有的S/N和空间分辨率测量碳和氮的临界发射线，最终目标是量化低质量和中等质量恒星中这些元素的产生。我们的样本是从PNe中选择的，具有接近太阳的金属丰度，但在N/O中跨越了很宽的范围。这项研究，一系列的第一个，集中在观测和发射线测量所得的积分沿整个空间范围的狭缝。我们推导了具有最强UV线检测的七个PNe（IC~2165、IC~3568、NGC~2440、NGC~3242、NGC~5315、NGC~5882和NGC~7662）的离子和总元素丰度。我们比较这些新的结果与其他最近的研究星云，并讨论了相对的优点，推导出的总元素丰度的C，N和O使用电离校正因子（ICF）与总丰度。对于具有最佳UV线检测的七个PNe，我们得出结论，来自具有可测量UV线的离子的直接诊断的总和丰度给出了C和N的总元素丰度的最准确值。在某些情况下，我们的丰度和其他研究之间存在显着的差异，我们表明，这些差异往往可以归因于他们使用的通量是不共空间。最后，我们研究了C/O和N/O与O/H和He/H在观测良好的银河系，LMC和SMC PNe，并发现，高度准确的丰度是必不可少的正确推断元素产量从他们的祖星。
英文摘要：
We present observations and initial analysis from an HST/STIS program to obtain the first co-spatial, UV-optical spectra of ten Galactic planetary nebulae (PNe). Our primary objective was to measure the critical emission lines of carbon and nitrogen with unprecedented S/N and spatial resolution over UV-optical range, with the ultimate goal of quantifying the production of these elements in low- and intermediate-mass stars. Our sample was selected from PNe with a near-solar metallicity, but spanning a broad range in N/O. This study, the first of a series, concentrates on the observations and emission-line measurements obtained by integrating along the entire spatial extent of the slit. We derived ionic and total elemental abundances for the seven PNe with the strongest UV line detections (IC~2165, IC~3568, NGC~2440, NGC~3242, NGC~5315, NGC~5882, and NGC~7662). We compare these new results with other recent studies of the nebulae, and discuss the relative merits of deriving the total elemental abundances of C, N, and O using ionization correction factors (ICFs) versus summed abundances. For the seven PNe with the best UV line detections, we conclude that summed abundances from direct diagnostics of ions with measurable UV lines gives the most accurate values for the total elemental abundances of C and N. In some cases where significant discrepancies exist between our abundances and those from other studies, we show that the differences can often be attributed to their use of fluxes that are not co-spatial. Finally, we examined C/O and N/O versus O/H and He/H in well-observed Galactic, LMC, and SMC PNe, and found that highly accurate abundances are essential for properly inferring elemental yields from their progenitor stars.
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