Collaborative Project: The Internal Kinematics of Dwarf Spheroidal Galaxies: Do They Contain Dark Matter? (Part I of 2 Projects)

在这项研究拨款中，将进行一系列广泛的成像和光谱观测和分析，旨在测试和测量矮小球状星系中假定的暗物质的分布。将首次测量LEO I和LEO II系统中恒星的速度色散或特征宽度。这些都是决定在其他矮小球状星系中测量到的大速度散布是由潮汐还是暗物质的存在造成的关键对象。我们已经收集了小熊座、神龙和六个矮星系的多纤维光谱数据。结合Fornax星系的梯形数据和新的观测，这些数据将允许确定这些星系的引力势，而不仅仅是它们的质量。对被认为不包含暗物质的遥远晕球状星团NGC2419的质光比的测量，将在评估矮小球状星系的质光比时提供必要的比较。为了改善或测量这些低光度星系的结构，已经收集了大量的成像数据。最后，将对一些有趣的射电源进行进一步的射电观测，但没有光学对应物。这个项目是与密歇根大学安娜堡分校的Mario Mateo博士合作的项目(AST 9223968)。

An extensive series of imaging and spectroscopic observations and analysis designed to test for and measure the distribution of the putative dark matter in dwarf spheroidal galaxies will be carried out in this research grant. The velocity dispersion, or characteristic width, of stars in the Leo I and Leo II systems will be measured for the first time. These are key objects for deciding if the large velocity dispersions measured in the other dwarf spheroidal galaxies are caused by tides or the presence of dark matter. Multifiber spectroscopic data have been collected for the Ursa Minor, Draco, and Sextan dwarf galaxies. Combined with echelle data for the Fornax galaxy and with new observations, these data will allow the gravitational potential of these galaxies, not just their mass, to be determined. Measurement of the mass-to-light ratio of the distant halo globular cluster NGC2419, which is thought to contain no dark matter, will provide a necessary comparison when assessing the mass-to-light ratios of the dwarf spheroidal galaxies. Extensive imaging data to improve or measure the structure of these low luminosity galaxies has been collected. Finally, further radio observations of some intriguing radio sources with no optical counterparts will be made. This project is a collaborative project with Dr. Mario Mateo of the University of Michigan at Ann Arbor (AST 9223968).