Proper motions of Milky Way Ultra-Faint satellites with Gaia DR2 x DES DR1
American Astronomical Society Winter Meeting contributed talk. Title: Proper motions of Milky Way Ultra-Faint satellites with Gaia DR2 x DES DR1 Abstract: We present a new, probabilistic method for determining the systemic proper motions of Milky Way (MW) ultra-faint satellites in the Dark Energy Survey (DES). We utilize the superb photometry from the first public data release (DR1) of DES to select candidate members, and cross-match them with the proper motions from Gaia DR2. We model the candidate members with a mixture model (satellite and MW) in spatial and proper motion space. This method does not require prior knowledge of satellite membership, and can successfully determine the tangential motion of most of the DES satellites. With our method we present measurements of the following satellites that lack spectroscopic follow-up: Columba I, Eridanus III, Grus II, Phoenix II, Pictor I, Reticulum III, and Tucana IV, the majority of which are the first systemic proper motion measurements. We compare these to the predictions of Large Magellanic Cloud satellites and to the vast polar structure. With the high precision DES photometry we conclude that most of the newly identified member stars are very metal-poor ([Fe/H] ≲−2) similar to other ultra-faint dwarf galaxies, while Reticulum III is likely more metal-rich. The members we find are excellent targets for future spectroscopic follow-up.