Comptonization of CMB in galaxy clusters. Monte Carlo computations

TL;DR

This paper develops a relativistic Monte Carlo simulation to model how the thermal Sunyaev-Zeldovich effect alters the CMB spectrum in galaxy clusters, revealing non-universal spectral shapes depending on photon directions.

Contribution

A novel Monte Carlo code for simulating relativistic Comptonization of the CMB, allowing detailed analysis of spectral and angular variations in galaxy clusters.

Findings

Spectral shape of the tSZ effect varies with photon escape directions.

The numerical results agree with analytical solutions and previous simulations.

The method can be applied to different cluster parameters and initial spectra.

Abstract

The problem under consideration is to determine the change of the Cosmic Microwave Background (CMB) spectral shape due to the thermal Sunyaev-Zeldovich 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.