The cosmological free-free signal from galaxy groups and clusters

TL;DR

This paper models the free-free radio emission from galaxy groups and clusters using simulations and analytical methods, showing potential for future detection to study the intracluster medium.

Contribution

It provides new insights into the free-free signals from massive haloes post-reionization, focusing on clusters and groups, which were less explored in previous models.

Findings

Massive haloes contribute less than 10% of the total free-free signal.

Individual signals from massive haloes could be detectable with future experiments.

The study compares simulation results with analytical predictions for validation.

Abstract

Using analytical models and cosmological N-body simulations, we study the free-free radio emission from ionized gas in clusters and groups of galaxies. The results obtained with the simulations are compared with analytical predictions based on the mass function and scaling relations. Earlier works based on analytical models have shown that the average free-free signal from small haloes (galaxies) during and after the reionization time could be detected with future experiments as a distortion of the CMB spectrum at low frequencies ($\nu <$ 5 GHz). We focus on the period after the reionization time (from redshift $z=0$ up to $z=7$) and on haloes that are more massive than in previous works (groups and clusters). We show how the average signal from haloes with $M > 10^{13} h^{-1} M_{\odot}$ is less than 10% the signal from the more abundant and colder smaller mass haloes. However, the individual signal from the massive haloes could be detected with future experiments opening the door for a new window to study the intracluster medium.