Distances to high-velocity clouds

ast -0607154机构：威斯康星大学麦迪逊分校pi: Bastiaan wakker标题：高速云的距离巴斯蒂安·瓦克（威斯康星大学麦迪逊分校）将与合作者蒂莫西·比尔斯博士（密歇根州立大学）、唐纳德·约克博士（芝加哥大学）和罗纳德·威廉博士（德克萨斯理工大学）一起进行一项计划，以确定到14个所谓的高速云（hvc）和中速云（IVCs）的距离。这些是巨大的中性氢气云，它们的移动速度与简单的星系旋转模型不相容。该目标将通过首先从中分辨率光谱中确定到蓝色水平分支（BHB）恒星沿视线的距离，然后在高分辨率光谱中寻找来自云的星际吸收特征来实现。通过确定哪些光谱揭示了云的特征，并知道从光谱中导出的恒星的距离，可以获得到云的距离的约束。这些云的距离仍然是银河系天文学中突出的问题之一，这些云的性质的解决将为星系形成和演化的模型提供重要的约束。这项工作将对天文学的各个子领域产生广泛的影响，特别是星系的形成和演化。该计划的组成部分是独立的，非常适合研究生和本科生的研究项目。还将开展外联活动。

AST-0607154INSTITUTION: University of Wisconsin, MadisonPI: Bastiaan WakkerTITLE: Distances to High-Velocity CloudsABSTRACTDr. Bastiaan Wakker (University of Wisconsin at Madison), along with collaborators Dr. Timothy Beers (Michigan State University), Dr. Donald York (University of Chicago) and Dr. Ronald Wilhelm (Texas Tech University), will undertake a program to determine the distances to 14 so-called high-velocity clouds (HVCs), and intermediate-velocity clouds" (IVCs). These are massive clouds of neutral hydrogen gas that are moving with velocities that are incompatible with simple models of galactic rotation. The goal will be accomplished by first determining the distances to blue horizontal branch" (BHB) stars along the line of sight from medium-resolution spectra, and then looking for interstellar absorption features from the clouds in high-resolution spectra. By determining which spectra reveal the signature of the clouds, and knowing the distances to the stars from which the spectra were derived, constraints on distances to the clouds can be obtained. Distances to these clouds remain one of the outstanding problems in Galactic astronomy, and resolution of the nature of these clouds will provide important constraints on models of galaxy formation and evolution.The work will have broad impact on various sub-fields of astronomy, particularly galaxy formation and evolution. Components of the program are self-contained, and well-suited for graduate and undergraduate research projects. Outreach activities will also be undertaken.