Contributions from Stellar Mixing and Primordial Enrichment to Globular Cluster Abundances

“恒星混合和原始富集物对球状星团丰度的贡献”球状星团是我们所认识的最古老的天体之一。确定它们的年龄对于设定宇宙年龄的限制至关重要。此外，由于它们的生命周期很长，在它们的组成恒星中包含了我们银河系化学史的“化石记录”。然而，情况比人们希望的要复杂得多。尽管球状星系团曾经被认为是化学上均一的物体，但光谱分析表明，同一星系团中最亮的红巨星通常在表面元素C-N-O-Na-Mg-Al上表现出丰度差异。这些差异中至少有一些似乎来自深度混合，在深度混合中，物质从燃烧氢的壳层附近输送到恒星表面。但除此之外，还有一些原始丰度，这些丰度是在一些星团恒星形成时设定的，这些气体是从前一个时代的大质量恒星中选择性地富含重元素形成的。目前的奖项着眼于一个主要目标，即测量星团中的红巨星的丰度，这些星团的金属贫化程度低于之前研究的那些星团。这将有助于研究金属丰度对深层混合过程的影响。深度混合作为恒星质量的函数也将被研究。原始效应对球状星团丰度不均匀的贡献程度将通过对其他几个球状星团中较暗的红巨星和主序星的光谱分析来研究。在这里，人们预计深度混合一直是一个有效的因素。用凯克望远镜和相关光谱仪进行的观测构成了这项工作的核心。解释将来自最先进的大气模型理论的应用。

Smith, Graeme" Contributions from Stellar Mixing and Primordial Enrichment to Globular Cluster Abundances "AST- 0098453Globular clusters are among the oldest objects that we recognize. Determinations of their ages are critical for setting limits to the age of the universe. In addition, because of their long lifetimes, they contain within their constituent stars a "fossil record" of the chemical history of our own galaxy. However, the situation is more complicated that one might hope. Although globular clusters were once thought to be chemically homogeneous objects, spectroscopy has shown that the brightest red giant stars within the same clusters commonly exhibit abundance differences in the surface elements C-N-O-Na-Mg-Al. At least some of these differences appear to arise from deep mixing in which material is transported from near the hydrogen-burning shell to the surface of the star. But over and above this, there are the primordial abundances which were set when some cluster stars were formed from gas which had been selectively enriched in heavy elements from high-mass stars of a former epoch. The present award looks to a main goal of measuring abundances of red giants in clusters that are less metal poor than those previously studied. This will allow the investigation of the effects of metallicity on the deep mixing process. Deep mixing as a function of stellar mass will also be investigated. The degree to which primordial effects have contributed to globular cluster abundance inhomogeneities will be investigated by spectroscopy of the fainter red giant stars and main sequence stars in several other globular clusters. Here one expects that deep mixing has been an effective agent. Observations with the Keck telescopes and associated spectrographs form the core of this work. Interpretation will follow from the application of state-of-the-art model atmosphere theory.