The objectives of this project are to use data from the European Space Agency’s Gaia satellite to determine the shape of the Milky Way’s dark matter halo and how it this shape changes with distance from the center. The background image shows Gaia’s multi-color map of the Milky Way and two nearby satellite galaxies, the Large and Small Magellanic Clouds (bottom right). This image is not a photograph but a map comprised of billions of individual stars in the Milky Way and its neighborhood. For this project the team will use data obtained by Gaia that gives positions and velocities for stars in the Milky Way’s halo along with the new computational modeling tools they are developing. They will use the fact that most halo stars travel through the halo on regular trajectories (like the one pictured by the blue curve) to compute conserved quantities (“actions”) for each of hundreds of thousands of stars. Modeling the motions of halo stars will allow the team to set constrains on the density profile and the shape of the Milky Way’s dark matter halo. By comparing their derived dark matter distribution with results from simulations they hope to shed light on the nature of the elusive dark matter particle.

The background image is a multi-color image of the Milky Way disk, its halo and nearby satellite galaxies obtained with the European Space Agency’s Gaia Satellite ( . The blue curve shows an example of (half) of a regular trajectory that a star in the halo of the Milky Way might follow

U-M Researchers

Monica Valluri

Other Researchers

Eugene Vasiliev (University of Cambridge

Pablo Fernández de Salas (University of Stockholm)

Katherine Freese (UT Texas and University of Stockholm)