Tomography of the interstellar medium at small scales

小尺度星际介质断层扫描

• 批准号: 25331161
• 负责人: Professor Dr. Klaas S. de Boer (†)
• 金额: --
• 依托单位: Institut für Physik und Astronomie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2006
• 资助国家: 德国
• 起止时间: 2005-12-31 至 2009-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/25331161?language=en
• 关键词: Tomography; interstellar; medium; small; scales

Measurements of the Galactic interstellar medium (ISM) in absorption and emission have demonstrated that significant small-scale structure exists at scales <10 pc. However, very little is know about the nature of this smallscale component of the ISM, because systematic investigations are extremely difficult in view of the small volume-filling factor of these structures. In particular, the discovery of a very small clump of gas in the Milky Way halo containing hydrogen molecules (H2) together with earlier suggestions of the existence of very compact cold clumps of gas indicates that perhaps a considerable amount of baryonic matter has thusfar remained undetected and that such material may account for a fair fraction of the hitherto elusive dark matter .In this project we want to study the ISM in the disk and halo of the Milky Way on small scales using optical and (far-)ultraviolet absorption spectra of stars in Galactic Globular Clusters and in the Magellanic Clouds. The analysis of a large number of sightlines distributed over a very small field of view (as in the case of a star cluster and the Magellanic Clouds) offers the unique possibility to systematically investigate the structure and physical properties of the nearby disk and halo ISM on small scales. The combined information about the spatial distribution and the radial-velocity distribution of the gas will provide a tomographic view of the small-scale interstellar medium. The distribution of sizes and densities (and perhaps the fractal dimension of the ISM) will allow to predict how many very small and dense clumps exist and how much mass they contain.

对银河系星际介质 (ISM) 吸收和发射的测量表明，在小于 10 pc 的尺度上存在显着的小尺度结构。然而，人们对 ISM 的这种小规模组成部分的性质知之甚少，因为鉴于这些结构的体积填充系数较小，系统研究极其困难。特别是，在银河系晕中发现了含有氢分子（H2）的非常小的气体团，以及早期关于存在非常致密的冷气体团的建议，这表明迄今为止可能有相当数量的重子物质尚未被发现，并且这种物质可能占迄今为止难以捉摸的暗物质的相当一部分。在这个项目中，我们想要研究银河系盘和晕中的ISM 使用银河球状星团和麦哲伦星云中恒星的光学和（远）紫外吸收光谱在小尺度上进行研究。对分布在非常小的视场（如星团和麦哲伦云）上的大量视线的分析提供了独特的可能性，可以在小尺度上系统地研究附近圆盘和晕ISM的结构和物理特性。有关气体空间分布和径向速度分布的综合信息将提供小尺度星际介质的层析图像。尺寸和密度的分布（也许还有 ISM 的分形维数）将允许预测存在多少非常小且密集的团块以及它们包含多少质量。