Wiggling Through the ICM: Multi-Resolution Radio Imaging of a Tailed Radio Galaxy in MACS J1354.6+7715

TL;DR

This study uses multi-frequency radio observations to analyze a tailed radio galaxy in MACS J1354.6+7715, revealing its dynamics, age, and interaction with the cluster environment, and providing insights into early cluster assembly.

Contribution

It presents detailed radio imaging and spectral analysis of a tailed radio galaxy, offering new insights into galaxy infall, AGN activity, and cluster dynamics during early assembly stages.

Findings

The tailed radio galaxy exhibits a 300 kpc tail with spectral steepening from -0.46 to -2.43.

Synchrotron modeling indicates a radiative age of 150 Myr and a galaxy velocity near 1956 km/s.

No relics or halos detected; X-ray data suggest a pre-merging, undisturbed cluster environment.

Abstract

Tailed radio galaxies are powerful tracers of interactions between active galactic nuclei (AGN) and the intracluster medium (ICM), providing unique insights into cluster dynamics. We present LOw Frequency ARray (LOFAR) 144 MHz and uGMRT 400 MHz observations of the cluster MACS J1354.6+7715 (z = 0.3967) to investigate the radio emission associated with its member galaxies and the cluster environment. The dominant tailed radio galaxy in the cluster exhibits a sharply bent tail extending over approximately 300 kpc, with the spectral index steepening from approximately -0.46 +/- 0.21 near the AGN core to approximately -2.43 +/- 0.30 in the outermost regions. Synchrotron modelling of the tail yields a radiative age of 150 +/- 10 Myr, implying a galaxy velocity of 1956 +/- 130 km s^-1, which is of order ~ 0.9 times the escape velocity. We find no evidence of relics or halos in our radio images, and the X-ray morphology from Chandra appears relatively undisturbed, suggesting that the system is a pre-merging candidate. Our results indicate that the radio galaxy is undergoing its first infall into the cluster, providing an excellent laboratory for studying the impact of the ICM on AGN activity and galaxy evolution, and demonstrating how multi-frequency radio observations of tailed galaxies can uniquely probe both AGN lifecycles and the early stages of cluster assembly.