Enhanced radio emission between a galaxy cluster pair

¹ INAF – IRA Via P. Gobetti 101 40129 Bologna, Italy
² George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University College Station TX 77843, USA
³ Leiden Observatory, Leiden University PO Box 9513 2300 RA Leiden, The Netherlands
⁴ Istanbul University, Faculty of Science, Department of Astronomy and Space Sciences 34116 Istanbul, Türkiye

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 11 August 2025
Accepted: 3 December 2025

Abstract

Context. Interacting pairs of galaxy clusters offer a unique opportunity to study the properties of the gas residing in the intracluster bridge connecting them. As a consequence of the encounter, both the X-ray and radio emission from the gas are expected to be enhanced by shocks and turbulence, facilitating their detection.

Aims. PSZ2 G279.79+39.09 is likely an off-axis merging system at z = 0.29 with its two main cluster components observed at a projected distance of ∼1.3 Mpc. In this paper, we investigate the presence of diffuse radio emission associated with the system.

Methods. We observed this cluster pair with the MeerKAT UHF band (544–1088 MHz) for 7.5 h and with the uGMRT band 3 (300–500 MHz) for 8 h. These are the first targeted radio observations of this system.

Results. We discovered diffuse synchrotron emission in the system, with an indication of enhanced emission in the region bridging the cluster pair. The detection is based on the MeerKAT UHF data, while the uGMRT band 3 observation does not allow us to derive a stringent limit on the spectral index of the source. This emission is likely generated by the turbulence injected as a consequence of the cluster-cluster encounter. However, the study of its physical properties is limited by the observations currently available for the target. If the two clusters have not yet collided, this emission will resemble the radio bridges observed in A399-A401 and A1758N-S.

Conclusions. Similarly to other systems with multiple cluster components studied in recent years, the analyzed cluster pair represents an appealing target to investigate the presence of nonthermal phenomena beyond the well-studied denser regions of the intracluster medium. While in this work we presented a new detection, our analysis underlines the need for multiband observations to fully understand these kinds of sources.