Contributions from Stellar Mixing and Primordial Enrichment to Globular Cluster Abundances

恒星混合和原初富集对球状星团丰度的贡献

• 批准号: 0098453
• 负责人: Graeme Smith
• 金额: $ 17.01万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-06-01 至 2006-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0098453&HistoricalAwards=false
• 关键词: Contributions; Stellar; Mixing; Primordial; Enrichment

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.

Smith，Graeme”Contributions from Stellar Mixing and Primary Enrichment to Globular Cluster Abundances“AST-0098453球状星团是我们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年龄的界限至关重要。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，情况比人们希望的要复杂得多。虽然球状星团曾经被认为是化学上均匀的天体，光谱学显示，同一星团内最明亮的红巨星通常在表面元素C-N-O-Na-Mg-Al上表现出丰度的差异，其中至少有一些差异似乎是由物质从氢燃烧的壳层附近转移到星星表面的深度混合引起的。但除此之外，还有原始丰度，这是在某些星团恒星形成时确定的，这些星团恒星是由气体形成的，这些气体选择性地富集了来自前一个时代的高质量恒星的重元素。本奖项的主要目标是测量星系团中红巨星的丰度，这些星系团比以前研究的星系团少金属。这将使调查的影响，金属丰度的深层混合过程。还将研究作为恒星质量函数的深度混合。原始效应在多大程度上导致了球状星团丰度的不均匀性，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进行研究。在这里，人们期望深度混合是一种有效的手段。凯克望远镜和相关光谱仪的观测构成了这项工作的核心。解释将遵循国家的最先进的模型大气理论的应用。