Stellar streams and dark substructure: the diffusion regime

Understand

The cold dark matter picture predicts an abundance of substructure within the Galactic halo.

• However, most substructures host no stars and can only be detected indirectly.
• Stellar streams present a promising probe of this dark substructure.
• These streams arise from tidally stripped star clusters or dwarf galaxies, and their low dynamical temperature and negligible self-gravity give them a sharp memory of gravitational perturbations caused by passing dark substructures.