Chemical Enrichment in Planetary Nebulae from A to Z (alpha to zinc)

行星状星云携带着它的渐近巨大分支星祖先的内部核过程和富集的记录，以及恒星的初始组成。行星状星云对由慢中子捕获（s过程）合成的原子核的银河系化学富集也有特别重要的贡献。在之前nsf支持的一个项目中，Dinerstein博士对银河系行星状星云进行了近红外光谱调查，发现在大约40%的探测源中，s过程产物Se和Kr大量自富集。这项研究建立了恒星中Sr - Zr （Z = 38-40）的“light-s”峰的富集特征。在早期工作的基础上，迪纳斯坦博士将把Se和Kr的研究扩展到其他本星系群的行星状星云，进入一个新的、金属丰度更低的区域。她还将通过高分辨率光学和红外光谱寻找“重s”峰的元素，Ba， Xe等。该项目的第三部分将是对行星状星云中铁峰元素的研究。虽然铁本身在行星状星云中被消耗成尘埃，但附近的元素锌几乎没有消耗，但却与恒星中的铁密切相关（除非金属丰度极低）。因此，将推导Zn/H丰度作为替代，以首次确定局部群行星状星云的Fe/H，并与α元素（如O和Ar）的丰度进行比较。最后，将研究气相Fe，以寻找单个星云内点对点的变化，以解决尘埃如何均匀地在行星状星云喷出物中凝聚和生存的问题。最后一项研究特别重要，因为尘气比的变化可能导致其他不均匀性并影响热平衡，这反过来可以解释光学复合谱线与碰撞激发谱线长期存在的丰度差异。这里的工作本质上是多学科的，将促进与实验室光谱学家的密切联系，以进行线识别，振荡器强度等，这项工作的结果可能有助于限制核截面和恒星演化计算。人们对使用行星状星云作为距离指示器和母星系暗物质探测器的兴趣也越来越大，这使得了解它们祖先的性质变得很重要。这些项目将培训研究生和本科生（他们将得到支持），这里开发的材料将成为奥斯汀独立学区“学术磁铁”公立学校教育/推广计划的一部分。

A planetary nebula carries a record of the internal nuclear processes and enrichment in its asymptotic giant branch star progenitor, as well as of the initial composition of the star. Planetary nebulae are also particularly important contributors to Galactic chemical enrichment for nuclei synthesized by slow neutron captures (the 's-process'). In a previous NSF-supported project, Dr. Dinerstein conducted a near-ir spectroscopic survey of Galactic planetary nebulae, and found substantial self-enrichment of the s-process products Se and Kr in about 40% of the detected sources. This study established the demographics of enrichment for the 'light-s' peak, traced by Sr - Zr (Z = 38-40) in stars.Building on this earlier work, Dr Dinerstein will extend the Se and Kr study to planetary nebulae in other Local Group galaxies, moving into a new, lower-metallicity regime. She will also search for elements of the 'heavy-s' peak, Ba, Xe, etc. via high-resolution optical and infrared spectroscopy. A third part of this project will be an investigation of Fe-peak elements in planetary nebulae. Although Fe itself suffers depletion into dust in planetary nebulae, the nearby element Zn undergoes little to no depletion yet closely tracks Fe in stars (except at extremely low metallicities). Therefore, Zn/H abundances will be derived as a surrogate to make the first Fe/H determinations of local group planetary nebulae to compare with abundances of alpha elements such as O and Ar. Finally, gas phase Fe will be investigated to search for point-to-point variations within individual nebulae to address the question of how uniformly dust condenses and survives in planetary nebula ejecta. This last study is particularly important as variations in the dust-to-gas ratio may lead to other inhomogeneities and affect the thermal balance which in turn may explain long standing abundance discrepancies from optical recombination lines versus collisionally excited lines.The work here is multidisciplinary by nature and will foster a close connection to laboratory spectroscopists for line identifications, oscillator strengths, etc., and the results of this work may help constrain nuclear cross sections and stellar evolution calculations. There also is growing interest in using planetary nebulae as distance indicators and probes of dark matter in their parent galaxies, making it important to understand the nature of their progenitors. These projects will enable the training of both graduate and undergraduate students (who will be supported) and materials developed here will be part of an education/outreach program to 'academic magnet' public schools in the Austin Independent School District.