The distribution of mass in dwarf galaxies and the structure of their ISM

这个项目的核心是有效地利用甚大阵列(VLA)对精心挑选的低质量(或矮星)和富含气体的星系样本进行HI测量，这些样本的柱子密度很低，光谱分辨率很高。他们的恒星盘将用深近红外(NIR)测光技术进行研究，主要使用拉帕尔马的INT。从我们(和其他人)以前的研究中自然产生的科学目标如下：-将通过得出高质量的旋转曲线来探索总体引力潜力。这促进了物质分解成(恒星和气体)重子和暗物质(DM)。-气态盘的大小对于矮小星系来说并不是很为人所知，它将被探索到可以实现的最低气柱密度。这是估计这类星系的总大小和质量的唯一手段。恒星盘的大小将使用近红外光度法来确定。这些将与气盘的大小进行比较。-无线电和光学观测也将被方便地用于进行质量分解，从而研究重子和暗物质成分的分布。-星际介质(ISM)的结构将使用HI数据立方体进行研究。特别是，将建立HI黑洞的统计数据，并研究它们的尺寸分布与盘厚度和引力势深度的关系。-利用恒星和气体成分的表面质量密度，将通过Toomre准则评估(过去和未来)恒星形成的条件。这将揭示外层气盘中没有恒星形成的问题。这些测量和分析将有效地结合在一起，以实现对富含气体的矮小星系的性质的全面了解。得到的质量分布和引力势提供了气盘结构的边界条件，即气泡的厚度和大小分布。我们最新开发的软件工具有助于实现这一目标，该工具允许推导出气态盘的三维结构。此外，恒星和气态盘的大小之间的关系将扩展到星系的低质量端。这是第一次进行这样的系统研究。

Central to this project is the efficient use of the Very Large Array (VLA) to carry out HI measurements of the disks of a carefully selected sample of low-mass (or dwarf) and gas-rich galaxies down to very low column densities and with high spectral resolution. Their stellar disks will be investigated with deep near-infrared (NIR) photometry, mainly using the INT at La Palma. The science goals, which naturally arise from our (and others ) previous studies, are as follows:- The overall gravitational potential will be explored by deriving high-quality rotation curves. This facilitates a mass decomposition into the (stellar and gaseous) baryonic and Dark Matter (DM). - The sizes of the gaseous disks, not very well known for dwarf galaxies, will be explored down to the lowest gas column densities achievable. This is the only means to estimate the total size and mass of this kind of galaxies. The sizes of the stellar disks will be determined using NIR photometry. These will be compared to the sizes of the gas disks.- The radio and optical observations will also be conveniently used to carry out mass decompositions, thereby studying the distribution of the baryonic and dark matter constituents.- The structure of the interstellar medium (ISM) will be investigated using the HI data cubes. In particular, the statistics of HI holes will be established, and their size distribution be studied with respect to the disk thicknesses and depth of gravitational potentials.- Using the surface mass densities of the stellar and gaseous constituents, the conditions for (past and future) star formation will be assessed via the Toomre criterion. This will shed light on the lack of star formation in the outer gaseous disks.These measurements and analyses will be efficiently combined such as to achieve an overall understanding of the nature of gas-rich dwarf galaxies. The derived mass distributions and gravitational potentials deliver boundary conditions for the structure of the gaseous disks, i.e. their thickness and size distribution of bubbles. Achieving this goal is facilitated by our newly developed software tools, which allows to derive the three-dimensional structure of the gaseous disks. Furthermore, the relation between the size of the stellar and gaseous disk will be extended to the low-mass end of galaxies. It is the for the first time that such a systematic study will be conducted.