Dark Matter in the Galaxy: Insights from the Dynamics of Stellar Streams

Abstract: Dark matter constitutes most of the matter in the Universe, yet its fundamental nature and distribution remain poorly understood. Stellar streams, formed through the tidal disruption of globular clusters and dwarf galaxies, provide powerful tracers of the Milky Way's gravitational potential and dark matter halo. In this review, we examine how stellar stream morphology and kinematics can constrain the halo's structure, shape, and substructure. We discuss key observational signatures, including stream gaps, spurs, and perturbations, and investigate five prominent streams: Sagittarius, GD-1, Palomar 5, Orphan-Chenab, and Cetus Polar. We summarize analytical, statistical, and Bayesian methods used to model stellar streams and infer dark matter properties, highlighting challenges arising from parameter degeneracies, incomplete observations, progenitor uncertainties, and time-dependent perturbations, particularly those associated with the Large Magellanic Cloud. Finally, we discuss how upcoming astrometric and photometric surveys, together with improved dynamical modelling, may strengthen constraints on the Milky Way's dark matter distribution and help distinguish between cold, warm, and self-interacting dark matter scenarios.