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

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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).