用宇宙中亮星的定量光谱法剖析星系
Dissecting Galaxies with Quantitative Spectroscopy of the Brightest Stars in the Universe
摘要：
测量星系的距离，确定它们的化学成分，研究它们的恒星星族的性质和它们的星际介质的吸收特性是现代河外天文学的基本活动，有助于了解星系的演化和膨胀的宇宙。宇宙中光学上最亮的恒星，光谱A和B的蓝超巨星，是实现这些目的的独特工具。它们的绝对视星等可达M_V = -9.5，是利用现代恒星光谱定量分析方法获得星系精确定量信息的理想对象。对单个蓝超巨星目标的光谱分析提供了关于化学丰度和丰度梯度的宝贵信息，这比从HII区域获得的信息更全面，因为它包括了更多的原子种类，而且也更准确，因为它避免了通常应用于本星系群以外的旋涡星系HII区域的强线研究中固有的系统不确定性。与此同时，光谱分析为每个超巨星目标提供了恒星参数和星际消光，这提供了一种非常精确的方法，通过一种新开发的方法来确定河外距离，称为通量加权重力-亮度关系（FGLR）。使用目前这一代的10米级望远镜，这些光谱研究可以达到10 Mpc的距离。新一代的30 m级将允许将这项工作扩展到30 Mpc，这是本地宇宙的一个相当大的体积。
英文摘要：
Measuring distances to galaxies, determining their chemical composition, investigating the nature of their stellar populations and the absorbing properties of their interstellar medium are fundamental activities in modern extragalactic astronomy helping to understand the evolution of galaxies and the expanding universe. The optically brightest stars in the universe, blue supergiants of spectral A and B, are unique tools for these purposes. With absolute visual magnitudes up to M_V = -9.5 they are the ideal to obtain accurate quantitative information about galaxies through the powerful modern methods of quantitative stellar spectroscopy. The spectral analyis of individual blue supergiant targets provides invaluable information about chemical abundances and abundance gradients, which is more comprehensive than the one obtained from HII regions, as it includes additional atomic species, and which is also more accurate, since it avoids the systematic uncertainties inherent in the strong line studies usually applied to the HII regions of spiral galaxies beyond the Local Group. Simultaneously, the spectral analysis yields stellar parameters and interstellar extinction for each individual supergiant target, which provides an alternative very accurate way to determine extragalactic distances through a newly developed method, called the Flux-weighted Gravity - Luminosity Relationship (FGLR). With the present generation of 10m-class telescopes these spectroscopic studies can reach out to distances of 10 Mpc. The new generation of 30m-class will allow to extend this work out to 30 Mpc, a substantial volume of the local universe.
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