Presentation #401.05 in the session “How Gaia Reveals the Galaxy’s Secrets: Results on the Galactic Scale, Part 1”.
The dwarf spheroidal galaxy of Sagittarius (Sgr) is the nearest and most prominent example of ongoing galactic cannibalism in the entire sky. The majority of its stars have been stripped from the main body due to tidal forces from the Milky Way (MW), and span a >360 deg great circle on the sky forming what is known as the Sgr stream. This structure is one of the best tracers of the MW’s potential well that we have, and yet, many of its features remain to be understood. Some of these, such the bifurcation of the stream or its kinematics, could be naturally explained if the Sgr progenitor was an inclined rotating disk in infall into the MW potential well, which has stocked the discussion of whether Sgr could be the remnant of a gas-rich late-type galaxy, eroded after several close passages through the MW halo. In this talk I will present a detailed study of the core of Sgr where, using machine learning techniques, we have combined the information provided by 3300 RR-Lyrae stars, more than 2000 spectroscopically observed stars and Gaia data to derive the full phase-space, i.e. 3D positions and kinematics, of more than 1.2 x 105 member stars. This has allowed us to study Sgr’s internal structure and kinematics with unprecedented detail and to compare our results with predictions from different N-body models, shedding light on Sgr’s past and future.