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10/29/15: SO/NOAO Joint Colloquium Series: Nitya Kallivayalil, Univ. of Virginia


Title: Proper Motions in Local Group: Next Generation Astrometry

A primary goal of "Near-Field Cosmology" is to test the Lambda+ cold dark matter model on small scales where tension between theory and data are mounting. For example, a better estimate of the total halo mass is important for deciding if the Milky Way has the expected number of massive (Fornax analog) satellites or has too few of of them, e.g., the "Too big to fail problem" (Boylan-Kolchin et al. 2011). The most reliable means by which to constrain the properties of the Milky Way dark halo is through assessing the 6-D phase space distributions of tracers of its gravitational potential. This requires accurate proper motions in addition to (generally known) radial velocities for field stars and satellites widely distributed throughout the halo. I will discuss the results of our efforts to obtain proper motions for a variety of tracers in the Milky Way halo, as well as our efforts to push further out into the Local Group, and to definitively constrain halo mass and shape, as well as the orbital histories of the tracers.

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