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

行星状星云中的化学富集从 A 到 Z（α 到锌）

• 批准号: 0708245
• 负责人: Harriet Dinerstein
• 金额: $ 38万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0708245&HistoricalAwards=false
• 关键词: Chemical; Enrichment; Planetary; Nebulae; alpha

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.

行星状星云记录了其渐近巨星分支星星的内部核过程和浓缩过程，以及星星的初始组成。 行星状星云也是银河系化学富集的重要贡献者，因为它们是由慢中子捕获（“S过程”）合成的。 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，并在大约40%的探测源中发现了s过程产物Se和Kr的大量自富集。 这项研究建立了恒星中Sr - Zr（Z = 38-40）追踪的“光-s”峰的富集人口统计学。在这项早期工作的基础上，Dinerstein博士将把Se和Kr的研究扩展到其他本星系群星系的行星状星云，进入一个新的低金属度区域。 她还将通过高分辨率的光学和红外光谱来寻找“重S”峰的元素，Ba，Ba等。 该项目的第三部分将是对行星状星云中Fe峰元素的研究。 虽然铁本身在行星状星云中会被消耗成尘埃，但附近的元素锌几乎没有消耗，但在恒星中会紧密地跟踪铁（除了极低的金属丰度）。 因此，Zn/H丰度将被推导出来作为替代，以进行本星系群行星状星云的首次Fe/H测定，并与α元素（如O和Ar）的丰度进行比较。 最后，气相Fe将被研究，以寻找单个星云内的点到点变化，以解决尘埃如何均匀地凝聚和存活在行星状星云喷出物中的问题。 这最后一项研究是特别重要的，因为尘埃-气体比的变化可能会导致其他不均匀性，并影响热平衡，这反过来又可以解释长期存在的丰度差异，从光学复合线与碰撞激发线。这里的工作是多学科的性质，并将促进密切联系，实验室光谱学家的线识别，振子强度等，这一工作的结果可能有助于约束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，这使得了解其祖先的性质变得重要。 这些项目将使研究生和本科生（谁将得到支持）的培训和材料在这里开发的将是一个教育/推广计划的一部分，在奥斯汀独立学区的“学术磁铁”公立学校。