MERGHERS Pilot: MeerKAT discovery of diffuse emission in nine massive Sunyaev-Zel'dovich-selected galaxy clusters from ACT

TL;DR

This pilot study demonstrates MeerKAT's effectiveness in detecting diffuse radio emissions in galaxy clusters, validating a new observational strategy for large-scale cluster surveys with promising detection rates.

Contribution

The paper introduces a successful pilot survey using MeerKAT to detect diffuse radio emissions in galaxy clusters, supporting the feasibility of a larger planned study.

Findings

70% detection rate of diffuse emission in observed clusters

12 diffuse emission detections, 11 of which are new

Detection of both relics and radio halos in multiple clusters

Abstract

The MeerKAT Exploration of Relics, Giant Halos, and Extragalactic Radio Sources (MERGHERS) survey is a planned project to study a large statistical sample of galaxy clusters with the MeerKAT observatory. Here we present the results of a 16--hour pilot project, observed in response to the 2019 MeerKAT Shared Risk proposal call, to test the feasibility of using MeerKAT for a large cluster study using short (0.2--2.1\,hour) integration times. The pilot focuses on 1.28\,GHz observations of 13 massive, low-to-intermediate redshift ($0.22 < z < 0.65$) clusters from the Sunyaev-Zel'dovich-selected Atacama Cosmology Telescope (ACT) DR5 catalogue that show multiwavelength indications of dynamical disturbance. With a 70 per cent detection rate (9/13 clusters), this pilot study validates our proposed MERGHERS observing strategy and provides twelve detections of diffuse emission, eleven of them new, indicating the strength of MeerKAT for such types of studies. The detections (signal-to-noise ratio $\gtrsim6$) are summarised as follows: two systems host both relic(s) and a giant radio halo, five systems host radio halos, and two have candidate radio halos. Power values, $k$-corrected to 1.4 GHz assuming a fiducial spectral index of $\alpha = -1.3 \pm 0.4$, are consistent with known radio halo and relic scaling relations.