PI: Christopher Palma, University of Virginia, email@example.com
Address: PO Box 3818, Charlottesville, VA 22903, USA
CoI: Michael H. Siegel, University of Virginia
CoI: Steven R. Majewski, University of Virginia
CoI: Richard J. Patterson, University of Virginia
Title: Spectroscopy of Extratidal Stars Associated with the Ursa Minor and Leo II Dwarf Galaxies
Abstract: We intend to continue our Ph.D. thesis explorations of the Ursa Minor (Palma's thesis) and Leo II (Siegel's thesis) dwarf galaxies with a spectroscopic effort that will simultaneously resolve four issues: (1) We will measure radial velocities to confirm the association of Ursa Minor and Leo II giant star and blue horizontal branch star candidates that we find outside the nominal tidal radii of these systems. (2) We will also determine whether these stars are bound to their parent systems (no expected variation in the radial velocities with position) or are in the process of being tidally stripped (should show a radial gradient in the radial velocities). If these stars are unbound, it casts doubt on the validity of the virial equilibrium assumption that is implicit in the conversion of velocity dispersion to mass-to-light ratio and the resulting assumption of large amounts of dark matter in these systems. (3) In both systems we will also refine the measured velocity dispersions with large samples of stars at much larger radii than previous studies. (4) Spectroscopy of candidate QSOs found in our Leo II fields will be used to select the best objects for establishing the absolute astrometric reference frame. The QSO measurements will greatly aid our effort to measure the absolute proper motion of Leo II with a combination of archival 200'' plates, KPNO 4-meter CCD data, and HST snapshot observations.
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360