Abstract

Contributed Talk - Splinter CompQuantum   (MW-2050)

Bridging microscopic and macroscopic cosmic ray transport in galaxies

Christoph Pfrommer
Leibniz-Institut für Astrophysik Potsdam (AIP)

Understanding the processes underlying galaxy formation is one of the most important challenges in astrophysics. Unresolved questions include the disconnect between the short time scale of gas collapse on small scales and the long time scale for galaxy evolution, as well as the mechanism responsible for ejecting mass, momentum, and energy out of galaxies (or preventing their infall) in a way that matches the observed scaling relations. Recent progress strongly suggests that cosmic rays may play a crucial role in controlling these processes in and around galaxies. However, the strength of cosmic ray feedback depends very sensitively on the dynamical coupling of cosmic rays to the background plasma. I will review how cosmic rays interact with and propagate through the magnetised plasma in the interstellar medium. In particular, I will highlight a new insight into how cosmic rays drive plasma waves unstable in such a way that they can scatter off the waves, thereby regulating the cosmic rays' transport speed and momentum transfer to the ambient plasma. Using global galaxy simulations of the multi-phase interstellar medium within the CRISP framework, I will then demonstrate that cosmic rays play a decisive role in the formation and evolution of spiral galaxies by providing feedback that regulates star formation and drives gas out in galactic winds. This argues that a complete understanding of galaxy formation necessarily implies a coarse grained model of kinetic plasma physics of cosmic ray-wave interactions that will be applied to global galaxy formation simulations.