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

行星状星云记录了其渐近巨型分支星体的内部核过程和丰度，以及恒星的初始组成。行星状星云也是由慢中子捕获合成的核的银河系化学浓缩(‘S过程’)的特别重要的贡献者。在之前由美国国家科学基金会资助的一个项目中，迪纳斯坦博士对银河系行星星云进行了近红外光谱测量，发现大约40%的探测到的来源中存在S过程产物Se和Kr的大量自浓缩。这项研究建立了由恒星中的锶-锆(Z=38-40)追踪的“轻S”峰的人口统计学特征。在这项早期工作的基础上，丁纳斯坦博士将把Se和Kr的研究扩展到其他局部群星系中的行星状星云，进入一个新的、低金属丰度的区域。她还将通过高分辨率光学和红外光谱分析寻找重S峰的元素，如巴、氙等。该项目的第三部分将调查行星状星云中的铁峰元素。尽管在行星状星云中，铁本身会枯竭成尘埃，但附近的元素锌几乎不会枯竭，而且与恒星中的铁密切相关(金属含量极低的恒星除外)。因此，锌氢丰度将作为替代，首次测定局部类行星状星云的Fe/H丰度，并与O、Ar等α元素的丰度进行比较。最后，将对气相Fe进行研究，以寻找单个星云内的点到点的变化，以解决行星状星云喷出的均匀尘埃如何凝结和存活的问题。最后一项研究特别重要，因为尘气比的变化可能会导致其他不均匀，并影响热平衡，这反过来可能解释光学复合线与碰撞激发线之间长期存在的丰度差异。这项工作本质上是多学科的，将促进与实验室光谱仪在谱线识别、振子强度等方面的密切联系，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探测其母星系中暗物质的兴趣也越来越大，这使得了解它们的祖先的性质变得重要。这些项目将对研究生和本科生(他们将得到支持)进行培训，这里开发的材料将成为奥斯汀独立学区公立学校教育/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.