Speaker
Description
New generations of interferometers are revealing a wealth of spectacular filaments in the surrounding of radio galaxies, mostly residing in group/cluster environment, whose origin is still unknown. Filamentary structures present new opportunities for studying the physical processes in the intracluster medium, including their magnetic structures and the propagation of cosmic rays. Given the steep radio spectra shown by these structures, deep, low-frequencies observations are necessary to detect them. In this talk, I will present the deepest (56 hours) LOFAR-VLBI observations of filaments in the merging galaxy cluster Abell 2255 at 144 MHz. Going down to sub-arcsecond, we detected and resolved for the first time several filamentary structures related to the tailed cluster radio galaxies, characterizing their morphology and emission at unprecedentedly high-resolution (De Rubeis et al. 2025). These observations prove the potentiality of LOFAR-VLBI for studying these new emerging radio phenomenon. I will then present high-resolution spectral studies, that were possible combining LOFAR-VLBI data with the higher frequencies ones from uGMRT and VLA. With high-resolution (2-3 kpc), we can disentangle the spectral properties of the filaments to study their nature and the interplay between the radio galaxy and the turbulent cluster environment.
I will discuss several formation scenarios regarding the origin of the filamentary emission, involving future updates on this work thanks to new incoming radio and X-ray data, as well as comparison with other similar cases found for other galaxy clusters.
