A numerical study of the hadronic gamma ray emission from cosmic ray protons in radio jets

This thesis is a numerical study of the gamma ray emission from clusters and it is aimed at constraining the cosmic ray content of jets from radio galaxies. It involves the simulation and numerical analysis of Lagrangian tracers injected by the jets from radio galaxies into the Intracluster Medium evolving in a cosmological simulation. I have analyzed different sets of radio jet simulations, in which the cosmic rays are transported into the ICM. The jet simulations encompasses a single radio galaxy (Vazza et al (2021) A&A), a single radio galaxy with varying powers (Vazza et al (2023) A&A) and multiple radio galaxies (Vazza et al (2023) Galaxies). I have utilized Lagrangian tracers within the simulations to monitor the transport of cosmic rays originating from the radio jets into the ICM. I have calculated the gamma-ray flux under various radio jet conditions and compared it with the observational data from FERMI LAT. This comparative analysis has enabled me to establish constraints on the allowed cosmic ray energy content in the radio jets. I concluded that if radio galaxies have multiple bursts, then they violate the FERMI limit. In my simulations, for N_burst = 4, the gamma-ray flux surpasses the FERMI limit. Therefore, this can be used to limit the cosmic ray energy budget to be ≤ 25% of magnetic field energy in radio jet. This is due to the fact that the initial conditions have an equality between cosmic ray energy and the magnetic field energy. In my thesis I also proved that such limits hold for even variations of the initial jet power. Since neutrino and gamma ray flux are linked by the same process, in my thesis as an additional task I also focus on the injection of neutrinos diffused into the clusters of galaxy by hadronic collision and comparing the neutrino flux with the observational results of IceCube. Overall my thesis has shown that gamma-ray and neutrino data can be used to refine existing physical models of radio jets in clusters of galaxies.