The MeerKAT Massive Distant Clusters Survey: A Radio Halo in a Massive Galaxy Cluster at z = 1.23

TL;DR

This paper reports the discovery of the highest redshift radio halo at z=1.23 in a galaxy cluster, confirming rapid magnetic field amplification in early universe clusters and supporting turbulent re-acceleration models.

Contribution

It presents the first detection of a radio halo at z > 1, expanding the known redshift range of such phenomena and providing new insights into magnetic field evolution in galaxy clusters.

Findings

Detected a radio halo at z=1.23, the highest redshift to date.

Measured a spectral index of 1.3 ± 0.4 for the radio halo.

Derived a radio power of (4.4 ± 1.5) × 10^{24} W Hz^{-1}.

Abstract

In the current paradigm, high redshift radio halos are expected to be scarce due to inverse Compton energy losses and redshift dimming, which cause them to be intrinsically faint. This low occurrence fraction is predicted by cosmic ray electron turbulent re-acceleration models. To date, only a handful of radio halos have been detected at redshift z > 0.8. We report the MeerKAT detection of a radio halo hosted by a galaxy cluster ACT-CL J0329.2-2330 at z = 1.23, making it the highest redshift halo detected thus far. Using L-band and UHF-band observations, we derive a radio halo spectral index of $\alpha^{1.3GHz}_{0.8GHz}$ = 1.3 $\pm$ 0.4 and a radio power of P$_{1.4GHz}$ = (4.4 $\pm$ 1.5) $\times$ 10$^{24}$ W Hz$^{-1}$. This result further confirms that there is rapid magnetic field amplification in galaxy clusters at high redshift.