Collaborative Research: On the Origin of Abundance Inhomogeneities in Globular Clusters

合作研究：球状星团丰度不均匀性的起源

• 批准号: 0908757
• 负责人: Graeme Smith
• 金额: $ 32.86万
• 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: 2009
• 资助国家: 美国
• 起止时间: 2009-09-15 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0908757&HistoricalAwards=false
• 关键词: Collaborative; Research; Origin; Abundance; Inhomogeneities

In this collaborative program, Dr. Michael Briley (University of Wisconsin - Oshkosh) and Dr. Graeme Smith (University of California - Santa Cruz) will undertake a detailed study of the abundances of various elements in globular cluster stars. It has long been known that stars in an individual cluster all have the same abundance of iron and other heavier elements, but have inhomogeneous abundances in a handful of light elements such as carbon, nitrogen, oxygen, sodium, magnesium, and aluminum. Astronomers now realize that these variations result from an abundance altering process which operates during red giant branch ascent (i.e., some form of deep mixing missing from canonical stellar models) superimposed on primordial variations from the era of star formation. The research team will obtain spectra of CH and CN absorption bands in the violet spectral region, as well as absorption lines from sodium, magnesium, and aluminum at visible-red wavelengths. There are three main goals to the project: to examine the onset and extent of mixing-induced carbon depletion as a function of iron abundance; to measure the fraction of CN-enhanced stars as a function of cluster mass and apparent shape, thereby probing the effects of environment on primordial abundance variations; and to broaden the range of globular clusters in which light element variations have been studied. This project will directly support the training of a graduate student at UCSC and undergraduate students at UW Oshkosh (an undergraduate research institution), who will be directly involved in all aspects of the project. Public outreach and education will be enabled through public talks to schools, clubs, and civic organizations, as well as the development of a presentation for the visitor's gallery of the Lick 3-m telescope that will describe how spectroscopy is used to determine the chemical abundances of stars, and why globular clusters in particular yield an astronomical fossil record of the chemical evolution of galaxies.

在这一合作方案中，Michael Briley博士（威斯康星州-奥什科什大学）和Graeme Smith博士（加州大学-圣克鲁斯）将对球状星团恒星中各种元素的丰度进行详细研究。 人们早就知道，单个星团中的恒星都有相同的铁和其他重元素丰度，但有少数轻元素的丰度不均匀，如碳，氮，氧，钠，镁和铝。天文学家现在意识到，这些变化是由红巨星分支上升过程中的丰度变化过程造成的（即，某种形式的深混合失踪的典型恒星模型）叠加在原始的变化，从时代的星星形成。 研究小组将获得紫色光谱区域的CH和CN吸收带的光谱，以及可见红光波长的钠，镁和铝的吸收线。 该项目有三个主要目标：研究混合引起的碳贫化的开始和程度，作为铁丰度的函数;测量CN增强型恒星的比例，作为星团质量和表观形状的函数，从而探测环境对原始丰度变化的影响;扩大已研究轻元素变化的球状星团的范围。该项目将直接支持UCSC的研究生和UW Oshkosh（本科研究机构）的本科生的培训，他们将直接参与项目的各个方面。将通过对学校、俱乐部和民间组织的公开讲座，以及为利克3米望远镜的游客画廊制作一个介绍，介绍光谱学如何用于确定恒星的化学丰度，以及为什么球状星团特别产生星系化学演化的天文化石记录，来实现公众宣传和教育。