Mapping the Stellar Halo with the H3 Spectroscopic Survey

Understand

Modern theories of galaxy formation predict that the Galactic stellar halo was hierarchically assembled from the accretion and disruption of smaller systems.

• This hierarchical assembly is expected to produce a high degree of structure in the combined phase and chemistry space; this structure should provide a relatively direct probe of the accretion history of our Galaxy.
• Revealing this structure requires precise 3D positions (including distances), 3D velocities, and chemistry for large samples of stars.
• The Gaia satellite is delivering proper motions and parallaxes for >1 billion stars to G~20.