Speaker: Sarah Pearson (NBI)

Title: Decoding Dark Matter with Stellar Streams from Beyond the Milky Way

Abstract: Upcoming and ongoing surveys will enable the detection of thousands of stellar streams around external galaxies. These streams form when dwarf galaxies or star clusters are tidally disrupted by their host gravitational potentials, producing elongated structures of stars with coherent, ordered motion. In this talk, I discuss recent advances in the study of extragalactic stellar streams and their implications for dark matter. I introduce X-Stream, a generative framework that translates stream imaging into constraints on the radial density profiles of dark matter halos, from the inner regions out to the virial radius. X-Stream employs the GPU-accelerated, JAX-based code streamsculptor to generate thousands of stream realizations in trial gravitational potentials, coupled with nested sampling to efficiently explore the parameter space. The resulting halo constraints provide a powerful test of alternatives to cold dark matter, such as self-interacting dark matter, which predicts cored density profiles. In addition, constraints on the outer halo slope, which are expected to correlate with merger history in cosmological simulations, remain largely unexplored observationally. I discuss how extragalactic stream observations can be interpreted in the context of time-evolving dark matter halos. Finally, I present Potamides, a rapid stream-curvature–based method that uses projected stream morphologies to constrain the shape and barycenter of host galaxy potentials, jointly probing baryonic and dark matter distributions. With upcoming missions such as Euclid, the Rubin Observatory, and the Roman Space Telescope, extragalactic stellar streams will enable detailed dark matter mapping across thousands of galaxies.

• Date:
  Jan. 15, 2026, 2:30 p.m. – 3:30 p.m.
  
  
• Location:

  AIP; Kirch building, Conference room

  
  
• Contact:
  Ewald Puchwein
  epuchwein@aip.de