Cosmic dance in the Shapley Concentration Core. II. The uGMRT-MeerKAT view of filaments in the brightest cluster galaxies and tailed radio galaxies in the A3528 cluster complex

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Superclusters represent the largest-scale environments where a number of galaxy clusters interact with each other through minor and major mergers and grow via accretion along cosmic filaments. We focus on the in the core of the Shapley Supercluster ($z This chain includes three clusters: A3528 (which is itself composed of two sub-clusters, namely A3528N and A3528S), and A3532 and A3530, which present a mildly active dynamical state. We study how minor mergers affect the evolution of radio galaxies and whether they are able to re-accelerate relativistic electrons in the intracluster medium (ICM). To reveal these energetic processes, extremely sensitive radio observations are required. We used observations from the upgraded Giant Metrewave Radio Telescope (uGMRT) in Band 3 (250--500 MHz), Band 4 (550--900 MHz), and Band 5 (1000--1460 MHz), and MeerKAT L-band (900--1670 MHz) to obtain images and spectral index maps over a wide frequency band and spatial resolutions of the We reached noise levels of $ $, and $ $ for uGMRT Band 3, Band 4, Band 5, and MeerKAT L-band, respectively. For a comparison with the thermal ICM emission, we also used data from the Spectrum Roentgen Gamma (SRG)/eROSITA X-ray telescope. We detect faint diffuse radio emission associated with the radio galaxies in the In particular, the brightest cluster galaxies (BCGs) in A3528S and A3532 show filaments of diffuse radio emission that extend for $ kpc out of the radio galaxy. The spectral index of these filamentary structures is extremely steep and almost constant ($ Contrary to the radio tails in A3528N, the spectral properties of these radio filaments are not consistent with standard models of plasma ageing. We also detect roundish diffuse radio emission around the BCG in A3528S, which could be classified as a radio mini halo. The radio tail in this cluster appears longer than in earlier detections, being $ 300$ kpc long at all frequencies. We linked the presence of extended radio emission in the form of filaments and threads in the with the effect of minor mergers. This is also reinforced by the increasing X-ray fluctuations in correspondence with the radio extended emission in A3528S. Although less energy was involved, our findings support the hypothesis that these events can re-energise plasma originating from radio galaxies.