KIPAC Tea Talk: Exploring a cosmic ray inverse-Compton origin to the SZ-to-X-ray pressure deficit in the cool core cluster ZwCl 3146

Abstract: Our group has recently proposed the possibility that inverse-Compton scattering of CMB photons by ~GeV cosmic rays (CR-IC) injected by central AGN in cool core galaxy clusters produces a non-negligible continuum-like X-ray signal that is easily misinterpreted as ICM thermal bremsstrahlung continuum. This is particularly relevant to the cooling flow problem—the lack of star formation relative to X-ray-inferred ICM cooling rates. We have explored this possibility in the ZwCl 3146 cluster by comparing pressure profiles derived via X-rays and the thermal SZ effect, since while SZ measurements probe only thermal ICM electrons, additional CR–IC emission would appear to boost the X-ray–inferred pressure. In this talk, I will provide an overview of our results, which establish that non-negligible CR-IC emission is plausible in ZwCl 3146, and discuss future detailed work needed to robustly assess whether CR-IC could be relevant to the cooling flow problem.