Collisionless shocks around the largest structures

Zoom link: https://us02web.zoom.us/j/89236785442

Collisionless shocks around the largest structures

Uri Keshet, Ben Gurion University

Pristine collisionless shocks were recently detected around galaxy clusters - the largest objects ever to virialize, forming representative island universes on the nodes of the cosmic web. Although collisionless shocks were anticipated in the 1950s, we still have no self-consistent model for these natural particle accelerators, which boost charged particles to ultra-relativistic cosmic rays. Galaxy clusters, too, pose major open questions, with no self-consistent models for their global cooling stability, extended non-thermal emission, and unexpected spiral dynamics. I will outline our understanding, challenges, and new hints for both collisionless shock and galaxy cluster physics.