Damped Lyman Alpha Systems as Probes of Nitrogen Synthesis in the Early Universe

这个项目将使用阻尼莱曼-阿尔法系统(DLA)作为早期宇宙化学演化的探针来研究氮的起源。基本的不确定性是，主要的贡献是来自演化较慢的恒星，它们通过行星星云喷射物质，最终形成白矮星，还是来自更大质量的恒星，它们快速演化，通过超新星爆炸传播比氢和氦更重的元素。这两个过程的速度差异是研究的关键：低质量恒星分配元素所需的时间是DLA年龄的重要组成部分，DLA是低金属丰度和高红移的吸收线系统。研究人员将对详细的化学演化模型进行数值计算，并将其与同事提供的观测结果进行比较。一些特别好的观测到的DLA将被用来约束恒星形成历史。这项研究还将测试DLA性质的分布与初始恒星质量函数的特征或与第三族核合成的影响有关的想法。对天文学的一个重大贡献将继续是基于它们的预测成功对已发表的恒星产额进行关键评估，这是这位研究人员特别注意的一项活动。这项工作将影响我们对一种丰富的、具有生物重要性的元素的理解。这项研究将产生一篇博士论文，并将加强美国和海外的合作。

AST-0307118HenryThis project will study the origin of Nitrogen using damped Lyman-alpha systems (DLAs) as probes of chemical evolution in the early Universe. The basic uncertainty is whether the principal contribution comes from slower-evolving stars which eject material via planetary nebulae and end as white dwarfs, or more massive stars which evolve rapidly and spread elements heavier than hydrogen and helium by ending with a supernova explosion. The difference in speed of these two processes is the key to the investigation: the time it takes a lower-mass star to distribute elements is a significant fraction of the age of DLAs, which are absorption-line systems of low metallicity and high redshift. The researcher will numerically calculate detailed chemical evolution models and compare them to observations provided by colleagues. Some especially well-observed DLAs will be used to constrain star formation histories. This study will also test ideas relating the distribution of DLA properties either to characteristics of the initial stellar mass function, or to the effects of Population III nucleosynthesis.A significant contribution to astronomy will continue to be the critical evaluation of published stellar yields based on their predictive success, an activity for which this investigator is particularly noted. This work will affect our understanding of an abundant and biologically important element. The research will result in one doctoral dissertation and will enhance collaborations both in the US and abroad.***