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.

在吸收和发射中，银河盘中培养基（ISM）的测量表明，在尺度小于10 pc的尺度上存在显着的小规模结构。但是，对ISM的这个小规模组成部分的性质知之甚少，因为鉴于这些结构的较小体积填充因子非常困难。特别是，发现在银河系中发现了一小块气体含氢分子（H2）的气体（H2）以及早期的建议以及存在非常紧凑的冷水团块的建议，也许可能会遇到相当多的baryonic物质，因此未被发现了，这种材料可能会占据这种材料的范围，并且该材料可能会说明这一过程的相当一部分。在小尺度上，使用银河球状簇和麦哲伦云中的恒星的光学和（远）紫外吸收光谱。对大量视线分布在非常小的视野（如星形群和麦哲伦云的情况下）的分析提供了系统地研究附近磁盘的结构和物理特性的独特可能性，而Halo ISM在小尺度上。有关气体的空间分布和径向速度分布的组合信息将提供小规模星际介质的层析成像视图。尺寸和密度的分布（也许是ISM的分形维度）将允许预测存在多少个非常小且密集的团块，以及它们包含多少质量。