CfA Colloquium Schedule Fall 2005
 15 December 2005

15 December 2005

Speaker: Mario Mateo (University of Michigan)

Title: The Darkest Galaxies: Kinematics and Dark Matter in the Dwarf Spheroidal Satellites of the Milky Way

Abstract: I will present results from an ongoing project to obtain high-precision kinematic data for individual stars in many of the nearby Dwarf Spheroidal galaxy satellites of the Milky Way. The project uses echelle fiber spectrographs at Magellan (MMFS) and the MMT (Hectochelle) and has so far amasses over 4000 spectra of faint red giants in and around Leo I, Fornax, Carina, Draco, Sculptor and Sextans. The resulting velocity dispersion profiles are remarkably flat out to and in some cases somewhat beyond the King tidal radii defined by the stellar distributions. The data have been analyzed using traditional dynamial techniques as well as using newly-developed statistical tools to extract the mass distributions of the galaxies non-parametrically. All methods agree that the mass distributions of the galaxies are considerably more extended than the visible stellar components under assumptions of spherical symmetry and isotropy. I will discuss our plans to extend our analysis as we try to relax these assumptions using both traditional and non-parametric analysis techniques. I will review our results -- which confirm the view that dSph galaxies are the darkest systems known -- in the context of other recent work on these surprisingly complex objects, and in terms of applications of CDM models on scales of individual galaxies and the Local Group.


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