Speaker
Description
Most ~1-10 GeV hadronic cosmic rays accelerated in star-forming galaxies will eventually escape the relatively dense ISM gas and leak into the circumgalactic medium (CGM). What happens to them thereafter and do they do anything important in this low density environment? I will show that these CRs are, in fact, important: using a new semi-analytic model we have developed over the last few years I will show that CRs, accumulated over the last few Gyr of star formation, contribute non-negligibly to the pressure (gradient) in the CGM of L* galaxies like the Milky Way. I will further demonstrate that the same CR population is important in maintaining the temperature of the CGM via streaming heating. Finally, I will show that the isotropic gamma-ray flux measured by Fermi receives a non-negligible contribution from hadronic emission of CRs in the CGM of all galaxies on our lightcone. IGRB measurements therefore constrain the parameters governing transport of ~1-10 GeV CRs in the CGM.
