Comptonization of CMB in galaxy clusters. Monte Carlo computations

Abstract

ABSTRACT The problem under consideration is to determine the change of the cosmic microwave background (CMB) spectral shape due to the thermal Sunyaev–Zeldovich (tSZ) effect. We numerically model the spectral intensity of the CMB radiation Comptonized by the hot intergalactic Maxwellian plasma. To this aim, a relativistic Monte Carlo code with photon weights is developed. The code enables us to construct the Comptonized CMB spectrum in a wide energy range. The results are compared with known analytical solutions and previous numerical simulations. We also calculate the angular distributions of the intensity of radiation emerging from the cloud, which show that the spectral shape of the tSZ effect is not universal for different directions of escaping photons. The numerical method can be applied to simulate the processes of Comptonization for different optical depths, temperatures, initial spectra of photon sources, and their spatial distributions, the obtained results may have implications on investigating the profiles of galaxy clusters.