Speaker
Description
Within the disk of the Milky Way, GeV-range cosmic rays (CRs) are known to be energetically comparable to other components in the interstellar medium, while TeV-PeV-range CRs are very minor. However, the situation should be different after such CRs have escaped the disk and propagate to the scales of the much more tenuous circumgalactic medium (CGM) and/or intergalactic medium (IGM). Depending on the CR diffusion coefficient, there will likely be regions in the CGM or IGM where GeV CRs cannot reach even within a Hubble time. We discuss the likelihood that TeV-range CRs can reach and be energetically important in the warm-hot IGM (WHIM) residing in cosmic filaments, while PeV-range CRs may do so for the cool, diffuse IGM permeating cosmic voids. Such CRs can potentially affect the rate of gas accretion onto halos and filaments and hence the cosmic star formation rate, the observability of the WHIM and/or the Ly alpha forest, and possibly measurements of some cosmological parameters. We also discuss multimessenger observational tests. As these effects depend to some extent on the nature of the CR sources, clarifying their identity can also be important for studies of galaxy evolution and cosmology.
