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

该项目的核心是有效利用甚大阵列（VLA）对精心挑选的低质量（或矮）和富含气体的星系样本的盘进行HI测量，直到非常低的柱密度和高光谱分辨率。它们的星盘将主要利用拉帕尔马天文台的INT进行深近红外测光研究。科学目标，自然产生于我们（和其他人）以前的研究，如下：-整体引力势将通过推导高质量的旋转曲线来探索。这有助于质量分解为（恒星和气态）重子和暗物质（DM）。- 对于矮星系来说，气体盘的大小并不是很清楚，将被探索到可达到的最低气柱密度。这是估计这类星系的总大小和质量的唯一方法。恒星盘的大小将使用近红外测光来确定。这些将与气体盘的大小进行比较。无线电和光学观测也将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。将使用HI数据立方体研究星际介质的结构。特别是，将建立HI洞的统计数据，并研究它们的大小分布与盘厚度和引力势深度的关系。使用恒星和气体成分的表面质量密度，通过Toomre标准评估（过去和未来）星星形成的条件。这些测量和分析将有效地结合起来，以便全面了解富含气体的矮星系的性质。导出的质量分布和重力势提供的边界条件的气体盘的结构，即它们的厚度和尺寸分布的气泡。我们新开发的软件工具有助于实现这一目标，该软件工具允许导出气体盘的三维结构。此外，恒星和气体盘的大小之间的关系将扩展到星系的低质量端。这是第一次进行如此系统的研究。

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.