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Coffee talks

Monday 04/12/2023 @ 14:30, Sala riunioni quarto piano e on-line (

Ardiana Bushi (University of Bologna, Bologna, Italy), "The head-tail radio galaxy and revived fossil plasma in ABELL 1775"

In the context of active galactic nucleus (AGN) origin, radio galaxies often show signs of interaction with the intracluster medium (ICM), resulting in wide-angle (WAT), narrow-angle (NAT), and head-tail morphologies depending on the bending of the jets. In this thesis, our focus is on studying the central region of Abell 1775, a galaxy cluster in an unclear dynamical state, situated at a redshift of z = 0.07203. This region hosts two giant radio loud elliptical galaxies, the southeastern one B1339+266B hosts a head-tail radiogalaxy that “breaks” at the position of a cold front detected in the X-rays, revived fossil plasma filaments, and central diffuse emission. This study aims to investigate and constrain the spectral properties and trends along the head-tail, as well as the study of the revived fossil plasma, to better understand the process of formation of the nonthermal phenomena in A1775. In this respect, we made use of LOFAR 144 MHz, new deep uGMRT 400 MHz, and 650 MHz radio data. We observe an overall steepening along the tail of the head-tail radio galaxy. The newly obtained radio color-color diagrams for this radio source compared with standard aging models, imply an ongoing particle re-acceleration in the outer regions of the tail. We speculate contamination from filaments emission in the inner tail. An unexpected increase in the brightness at the head of the tail was observed indicating a complex bending of the jets near the head. In general, we observed a decrease of the estimated equipartition magnetic field, luminosity, and minimum pressure as moving farther from the head along the tail. Based on the low-frequency spectral index analysis we conclude that F1 and F2 filaments have an ultra-steep spectrum with ? > 2. We show that high sensitivity and high-resolution observations at low frequencies are fundamental for unveiling the complex structures and properties of tails and revived fossil plasma in the ICM.