Contributions from Stellar Mixing and Primordial Enrichment to Globular Cluster Abundances

《恒星混合和原始富集对球状星团丰度的贡献》，球状星团是我们所认识到的最古老的天体之一。确定它们的年龄对于确定宇宙的年龄是至关重要的。此外，由于它们的寿命很长，它们的组成恒星中包含了我们银河系化学历史的“化石记录”。然而，情况比人们所希望的要复杂得多。虽然球状星团一度被认为是化学性质均匀的物体，但光谱学表明，在同一星团中最亮的红巨星通常在表面元素C-N-O-Na-Mg-Al中表现出丰度差异。至少其中一些差异似乎是由于物质从燃烧氢的壳层附近被运送到恒星表面的深度混合造成的。但除此之外，还有一些原始的丰度，这些丰度是在一些星团由气体形成时确定的，这些气体被选择性地富集了来自前一个时期大质量恒星的重元素。目前的奖项的主要目标是测量红巨星的丰度，这些红巨星的金属含量比以前研究过的要少。这将允许研究金属丰度对深度混合过程的影响。作为恒星质量函数的深度混合也将被研究。原始效应对球状星团丰度不均匀性的影响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学研究。在这里，人们期望深度混合是一种有效的媒介。凯克望远镜和相关光谱仪的观测构成了这项工作的核心。随后将应用最先进的模式大气理论进行解释。

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.