Abstract

Contributed Talk - Splinter Multimessenger

Cosmic ray feedback 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 and circumgalactic media and how we can observationally test these theoretical considerations using new high-sensitivity MeerKAT observations. 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. Comparing cosmic ray spectra of electrons and protons to observational data and studying the correlation of the far-infrared emission with gamma-ray and radio emission from galaxies enables us to test the cosmic ray feedback models. This argues that a complete understanding of galaxy formation necessarily includes these non-thermal components.