Prof Wyn Evans (University of Cambridge)

The talk discusses discoveries in data from the Gaia satellite, which is scanning the sky right now. Gaia provides distances, velocities and chemical information on all stars brighter than 20th magnitude. With such precise chemistry and kinematics, we can uncover the accretion history of the Galaxy, including the build-up of stars and dark matter in the halo. This has led to two important discoveries with implications for dark matter detection experiments. First, a dark matter hurricane is blowing past the Solar system right now, associated with the newly-found S1 stellar stream. It offers new prospects of identifying the nature of the elusive dark matter particle, especially for detectors with directional sensitivity. Second,  a substantial fraction of the stellar and dark halo lies in an elongated structure called the Gaia Sausage. This head-on merger with a massive dwarf satellite 8 or so billion years ago re-configured the inner Galaxy, with consequences for the velocity distribution of dark matter particles,The Sausage skin has a tell-tale signature in indirect dark matter detection experiments. The Sausage Galaxy itself re-structured the Galactic disk, creating the thick disk, while its black hole scoured out the Galactic centre.

In Tolansky T125.