[Séminaire CosmoObs] CHEX-MATE: Unveiling the connection between Cluster Mergers and Diffuse Radio Emission from Weak Lensing

by Lorenzo Ingoglia

Friday 5 Jun 2026, 14:00 → 15:00 Europe/Paris

grand Amphi (LPSC)

Diffuse, cluster-scale radio emission in the form of radio halos is supposed to trace turbulent regions in the intracluster medium of merging galaxy clusters. This is supported by X-ray observations, which reveal correlations between thermal and non-thermal components. However, not all merging systems exhibit giant radio halos, and the mechanisms governing the injection and dissipation of turbulence into particle acceleration during these highly energetic events remain unclear. To further probe the merging processes of galaxy clusters and the generation of non-thermal phenomena, we present a joint weak-lensing, X-ray, and radio analysis of galaxy clusters combining data from the CHEX-MATE sample with LOFAR and MeerKAT observations. By reconstructing weak-lensing mass maps and shear profiles from the AMALGAM2 shear catalogues, we investigate the projected dark matter distribution in clusters with and without diffuse radio emission.

Our study identifies 33 clusters with high weak-lensing signal-to-noise ratios, among which 21 host radio halos. Centre offsets, convergence peak counts, and stacked shear profiles all discriminate between cluster populations, in agreement with X-ray morphological classifications. Most notably, splitting the radio halo sample by emission size reveals that giant radio halos are preferentially associated with disturbed dark matter distributions, independently confirming the merger–radio halo connection without relying on the thermal gas as a tracer. These findings anticipate forthcoming synergies with the Euclid mission and the Square Kilometre Array, which will deliver deeper weak-lensing catalogues and wider low-frequency radio coverage.