Wiggling through the ICM: multiresolution radio imaging of a tailed radio galaxy in MACS J1354.6+7715

ABSTRACT Tailed radio galaxies are powerful tracers of interactions between active galactic nuclei (AGNs) 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 $\sim 300$ kpc, with the spectral index steepening from $\alpha \approx -0.46 \pm 0.21$ near the AGN core to $\alpha \approx -2.43 \pm 0.30$ in the outermost regions. Synchrotron modelling of the tail yields a radiative age of $150\pm 10$ Myr, implying a galaxy velocity of $1956 \pm 130$$\mathrm{km\, s^{-1}}$, which is of order $\sim 0.9$ times the escape velocity. We further found no evidence of relics or haloes 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.