Stellar streams as seismometers for dark matter subhaloes

The goal of this project is to measure how dark matter clumps on small scales in the Milky Way. The properties of these clumps, known as dark matter subhaloes, are different in different dark matter models. In particular, this project aims to constrain the mass of the warm dark matter particle up to ~10 keV. We will measure these subhaloes using stellar streams which form as globular clusters and dwarf galaxies tidally disrupt in the Milky Way. Once the stars are stripped from the stream, they roughly follow the orbit of their progenitor, forming thin bands of stars on the sky. The passage of a subhalo near the stream imparts velocity kicks to the stars, changing their orbits, which creates gaps and wiggles in the stream. To date, more than 100 streams have been observed in the Milky Way and many of these show signs of perturbations. On the modeling side, much work has been done to show how perturbed streams can be used to infer the properties of the dark matter subhaloes.
In this project, we will measure the properties of these dark matter clumps with two approaches we have developed. First, we will build a census of individual perturbers by fitting the most perturbed stellar streams. Second, we will infer the population of subhaloes by comparing the statistical properties of streams, i.e. the power spectrum of their densities and track variations, with libraries of simulations in different dark matter models. This project will make use of existing data from the S5 survey and Gaia DR3 and upcoming data from LSST, WEAVE, 4MOST, and Gaia DR4.