Blue Supergiants as Probes of Stellar and Galactic Evolution in the Local Group

蓝超巨星是恒星形成星系中视觉上最亮的正常恒星。目前这一代的大型望远镜有助于在本星系群内对这类天体进行高分辨率光谱分析。在本星系群的两个富含金属的巨型螺旋星系银河系和m31，以及两个缺乏金属的矮不规则星系小麦哲伦星云和NGC6822中，将对具有统计意义的物体样本进行分析。等离子体物理恒星大气模型的最新发展使我们能够使用蓝超巨星作为恒星和星系化学演化定量研究的通用工具。精确的恒星参数和对轻元素丰度的测定，将对大质量恒星在大范围化学成分范围内的演化模型施加严格的观测约束。银河系中许多重元素的丰度模式和梯度将被探测到比经典的H II区域分析更大的范围。这将为研究宇宙物质循环和所研究的四个星系的化学演化提供良好的观测基础。该项目还将允许校准和建立蓝超巨星作为宇宙距离阶梯第一步的光谱距离指示器。

Blue Supergiants are the visually brightest normal stars in star-forming galaxies. The present generation of large telescopes facilitates high-resolution spectroscopy of such objects within the Local Group of galaxies. Analyses of a statistically significant sample of objects in the two metal-rich giant spiral galaxies of the Local Group, the Milky Way and M 31, and in two metal-poor dwarf irregular galaxies, the Small Magellanic Cloud and NGC6822, will be performed. Recent developments in plasmaphysical stellar atmosphere modelling allow us to use blue supergiants as versatile tools for quantitative studies of stellar and galactochemical evolution. Precise stellar parameters and abundance determinations of the light elements will put tight observational constraints on evolution models for massive stars over a wide range of chemical composition. Galactic abundance patterns and gradients for numerous heavier elements will be probed to a far greater extent than possible by classical analyses of H II regions. These will provide a sound observational basis for the study of the cosmic cycle of matter and the chemical evolution of the four galaxies under study. The project will also allow to calibrate and establish blue supergiants as spectroscopic distance indicators on the first step of the cosmic distance ladder.