What can Gaia proper motions tell us about Milky Way dwarf galaxies?

Abstract

We present a proper-motion study on models of the dwarf spheroidal galaxy Sculptor, based on the predicted proper-motion accuracy of Gaia measurements. Gaia will measure proper motions of several hundreds of stars for a Sculptor-like system. Even with an uncertainty on the proper motion of order 1.5 times the size of an individual proper-motion value of ~10 mas/century, we find that it is possible to recover Sculptor's systemic proper motion at its distance of 79 kpc.

5 pages, 1 figure; to appear in the proceedings of the GREAT-ITN conference on "The Milky Way Unravelled by Gaia", Barcelona (Dec 1-5 2014)