Investigations of the Stellar and Cluster Populations of the Inner Galactic Halo

最近的研究表明，银晕的平坦度和银晕水平分支的形态（即红色和蓝色HB星的相对频率）随着离银中心的距离而变化。津恩博士和其他天文学家对球状星团系统的研究表明，这是由于光晕的复合性质造成的。内光晕的球状星团具有表明非常古老的特征。当这个老光晕群延伸到外围光晕时，在大的星系中心距离上，大多数星团属于一个单独的星群，称为年轻光晕。老光晕星团的特性表明，这个系统是银河系崩溃的遗迹，最终产生了星系盘和凸起，而年轻光晕的特性表明，它是一个或多个大型卫星星系（类似于大麦哲伦星云）的碎片，它们与银河系合并，并在此过程中被潮汐破坏。该奖项的研究旨在验证这一关于银河系晕的结构和形成的假设，并提供有关内部晕的有价值的信息，即使该假设需要被抛弃。对选定的天琴座RR变星样本的观测将表明内晕的恒星群是否在运动学上与老晕球状星团相似。太阳附近的光晕恒星样本将被检查，以证明它们是老光晕和年轻光晕的混合物。这些研究获得的结果将提供更详细的内晕图像以及球状星团系统与恒星晕之间的关系。因此，它们将进一步加深我们对银河系演化的理解。

9319229 Zinn Recent investigations have indicated that the flattening of the galactic halo and the morphology of the horizontal branch (i.e. the relative frequencies of red and blue HB stars) of the halo vary with distance from the galactic center. The work of Dr. Zinn and other astronomers on the system of globular clusters suggests that this is due to the composite nature of the halo. The globular clusters of the inner halo have characteristics that are indicative of very old ages. While this Old halo population extends into the outer halo, at large galactocentric distances, the majority of clusters belong to a separate population, termed the Young halo. The properties of the Old halo clusters suggests that this system is a relic of the collapse of the Galaxy that ultimately produced the galactic disk and bulge, while those of the Young halo suggest that it is the debris of one or more large satellite galaxy (similar to the Large Magellanic Cloud) that merged with the Milky Way and was tidally disrupted in the process. The research carried out with this award is designed to test this hypothesis for the structure and formation of the galactic halo and to provide valuable information on the inner halo even if the hypothesis needs to be discarded. Observations of a selected sample of RR Lyrae variable stars will indicate if the stellar population of the inner halo is kinematically similar to the Old halo globular clusters. Samples of halo stars near the Sun will be examined for evidence that they are a mixture of the Old and Young halos. The results obtained by these investigations will provide a more detailed picture of the inner halo and the relationship between the globular cluster system and the stellar halo. They will therefore further our understanding of the evolution of our galaxy.