The important role of cosmic ray transport physics in galaxy evolution

Philipp A. Kempski

Princeton University

Tuesday, December 6, 2022


NW17-218 Hybrid

PSFC Seminars

Abstract: Although negligible by number density, relativistic cosmic rays (CRs) are an energetically important component of the plasmas filling galaxies and galaxy clusters. As a result, they may play an important role in shaping large-scale galactic dynamics, for example by driving galactic winds and/or heating diffuse gas in galaxy halos. The impact of CRs on galaxy evolution depends strongly on the type of the electromagnetic fluctuations that scatter them and regulate their transport, which remains uncertain. As a result, “CR feedback” is one of the biggest unsolved puzzles in galaxy evolution. In this talk, I will discuss theoretical uncertainties in CR propagation and how CR spectra measured at Earth help us constrain their transport physics. I will then use a plausible mode of transport to consider the impact of CRs on the propagation of waves in low-collisionality plasmas, which has implications for the thermal evolution of intra-cluster media in galaxy clusters.