Detecting Dark Matter Subhalos Using Gaia-1 and Other Stellar Streams

Dark matter makes up approximately 85% of all matter in our universe, however due to its purely gravitational interaction, its nature is one of the biggest open questions in astronomy. Dark matter is predicted to come in the form of gravitationally bound clumps, subhalos. Different theoretical models of dark matter predict distinct abundances of low mass subhalos. While low mass subhalos are hard to detect, stellar streams, long ribbons of stars, are the most sensitive probe of subhalos due to their high gravitational sensitivity. We use a simulation of cold dark matter subhalos in a Milky Way-like galaxy to predict which of the dozens previously detected stellar streams in the Milky Way have had a higher chance of interaction with a subhalo. Specifically, we focus on the stellar stream Gaia-1 due to its large apocenter and stream length that gives it a high probability of having been impacted by subhalos in the past. We find 5 close interactions between Gaia-1 and subhalos of a mass larger than 10⁷ Msun in the last 1 Gyr. This analysis can be applied to other stellar streams and provide us with a robust ranking of stellar streams with high probable interactions and interpretation of future LSST observations.