College of Science

SEMINAR: Robyn Sanderson [Kapteyn Institute, University of Groningen]

Weighing and Measuring the Milky Way: Inferring the Galactic Gravitational Potential

Jan 23, 2014 10:50 AM to Jan 23, 2014 12:00 PM at Building 8, Room 241

Robyn SandersonThe distribution of dark matter in the Milky Way is an important constraint on many astrophysical theories, including the properties of dark matter and the process by which galaxies form. In spite of its importance, the shape and size of the Galactic dark matter halo is currently very poorly understood. The Gaia astrometric space mission, which successfully launched in December, will make huge strides in understanding the distribution of mass in our Galaxy by precisely measuring the positions and velocities of 150 million stars. Among these will be many stars in tidal streams, the scattered remnants left behind when the Milky Way's tidal forces tear apart smaller galaxies that pass nearby. I will show how Gaia's observations of stars in tidal streams can be used to infer the Galactic halo's total gravitational potential, by exploiting the natural clustering of stream stars' constants of motion (more specifically, their actions). Our preliminary tests with a simple model show that for the quality of data we expect from Gaia, the number of streams we expect to find in the Milky Way's halo is more than enough to determine the two parameters of a toy potential. I will discuss the expansion of the technique to more realistic models of the Galactic potential, and the prospects given improvements in data quality from complementary ground-based surveys.

10:50 a.m. Refreshments
11:00 a.m. Seminar