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

AST-0307118亨利这个项目将使用阻尼莱曼α系统（DLAs）作为早期宇宙化学演化的探针来研究氮的起源。 基本的不确定性在于，主要贡献是来自演化较慢的恒星，它们通过行星状星云喷射物质并最终成为白色矮星，还是来自质量更大的恒星，它们快速演化并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：低质量星星分配元素所需的时间是DLAs年龄的一个重要部分，DLAs是低金属含量和高红移的吸收线系统。 研究人员将数值计算详细的化学演化模型，并将其与同事提供的观测结果进行比较。 一些特别好观察的DLAs将被用来约束星星的形成历史。 这项研究还将测试与初始恒星质量函数的特征或星族III核合成的影响有关的DLA属性分布的想法。对天文学的一个重大贡献将继续是基于其预测成功的已发表恒星产额的关键评估，这是一项特别值得注意的活动。 这项工作将影响我们对一种丰富的生物学重要元素的理解。 这项研究将产生一个博士论文，并将加强在美国和国外的合作。

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.***