The Milky Way halo contains several thin, dynamically-cold stellar streams that likely formed from the tidal disruption of low-mass stellar systems like globular clusters. These streams are powerful tools for testing dark matter theories: streams will enable mapping the global structure of mass in the Galaxy, and are extremely sensitive to gravitational perturbations such as interactions with dark substructure. Recent data from the Gaia mission (DR2) have enabled a high-contrast view of the longest Milky Way thin stream, the GD-1 stream, and have revealed a number of under-densities and a "spur" of stars associated with one such density gap in this stream. The observed morphology of GD-1 (the gap and spur) is naturally reproduced in models of the stream that include an encounter with a massive (~10^6-10^8), dense perturber, and is not expected in simple simulations of the stream formation. I will show models of the stream and discuss ways to test the substructure encounter scenario. If confirmed, the GD-1 stream would provide the first direct dynamical evidence of dark substructure in the Milky Way halo.
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019