CHEX-MATE: Scaling relations of radio halo profiles for clusters in the LoTSS DR2 area

TL;DR

This study investigates the relationship between galaxy cluster mass and radio emission profiles at low frequencies, revealing that accounting for mass and redshift reduces scatter and highlighting the role of cluster dynamics and magnetic fields.

Contribution

It introduces a detailed analysis of the scaling relations between cluster mass and radio profiles, incorporating spatially resolved data and considering the impact of cluster dynamical status and magnetic fields.

Findings

Reducing scatter by a factor of ~4 when accounting for mass and redshift.

No strong evidence for a direct R_H-M relation, suggesting structure formation influences halo size.

Constraints on magnetic field dependence consistent with theoretical expectations.

Abstract

The thermal and non-thermal components in galaxy clusters have properties that, although shaped from different physical phenomena, can share some similarities, mainly driven by their halo mass and the accretion processes. Scaling relations have been proven to exist for both components and studied in X-ray (thermal) and radio (non-thermal) bands. At the radio wavelength, such investigations are so far limited to the integrated quantities (e.g. total power and mass). We aimed to investigate the scaling relations between the mass of a galaxy cluster and its radio emission at low frequencies, treating both the integrated and the spatially resolved quantities for a sample of well-selected targets. We crossmatched LoTSS DR2 and CHEX-MATE datasets in order to get the deepest and most homogeneous radio data of a representative sample of objects. We analytically derived the expected relation between the radio power ($P_{\nu}$) and radio surface brightness profile, and performed a comparison with observational results. We obtained that properly accounting for the mass and redshift dependence in the radio profile can reduce the overall scatter by a factor of $\sim 4$, with an evident residual dependence on the cluster dynamical status. We showed that assuming no relation between the halo size ($R_{H}$) and the cluster mass ($M$) allowed us to reconcile the observed radio profile mass scaling and the one predicted starting from the $P_{\nu}-M$ relation. We discuss the implications of a lack of $R_H-M$ relation, assessing possible systematics and biases in the analyses, and interpreting it as a natural consequence of the structure formation process. Finally, we also considered the role of the magnetic field in the $P_{\nu}-M$ relation, putting constraints on its dependence upon the cluster mass and finding consistent results with expectations from our radio power mass scaling.