# Expanding the sample of radio minihalos in galaxy clusters

## TL;DR

This study expands the sample of known radio minihalos in galaxy clusters, confirming their association with cool core properties and turbulence-driven electron reacceleration, and finds no strong link to overall cluster mass.

## Contribution

The paper reports three new minihalo detections, confirms five existing ones, and analyzes their correlation with cluster core properties, significantly enlarging the sample size for statistical studies.

## Key findings

- No strong correlation between minihalo radio luminosity and total cluster mass.
- Strong positive correlation between minihalo radio power and X-ray luminosity of cool cores.
- Minihalos are typically confined by cold fronts, supporting turbulence reacceleration models.

## Abstract

Radio minihalos are diffuse synchrotron sources of unknown origin found in the cool cores of some galaxy clusters. We use GMRT and VLA data to expand the sample of minihalos by reporting three new minihalo detections (A 2667, A 907 and PSZ1 G139.61+24.20) and confirming minihalos in five clusters (MACS J0159.8-0849, MACS J0329.6-0211, RXC J2129.6+0005, AS 780 and A 3444). With these new detections and confirmations, the sample now stands at 23, the largest sample to date. For consistency, we also reanalyze archival VLA 1.4 GHz observations of 7 known minihalos. We revisit possible correlations between the non-thermal emission and the thermal properties of their cluster hosts. Consistently with our earlier findings from a smaller sample, we find no strong relation between the minihalo radio luminosity and the total cluster mass. Instead, we find a strong positive correlation between the minihalo radio power and X-ray bolometric luminosity of the cool core (r<70 kpc). This supplements our earlier result that most if not all cool cores in massive clusters contain a minihalo. Comparison of radio and Chandra X-ray images indicates that the minihalo emission is typically confined by concentric sloshing cold fronts in the cores of most of our clusters, supporting the hypothesis that minihalos arise from electron reacceleration by turbulence caused by core gas sloshing. Taken together, our findings suggest that the origin of minihalos should be closely related to the properties of thermal plasma in cluster cool cores.