Seminar

[LasMañanasIFCA]"Probing radio restarting activity and duty cycle in high-energy selected giant radio galaxies" por Gabriele Bruni

Cross-correlating the INTEGRAL/IBIS and Swift/BAT AGN population with radio catalogs (NVSS, FIRST, SUMSS), we found that 25% of extended radio sources are Giant Radio Galaxies (GRG), i.e. the largest individual objects in the Universe. This fraction is four times more abundant than what has been found in previous studies. In 2014, we observed a pilot sample of these soft gamma-ray selected GRG at low radio frequencies with the GMRT, with the aim of studying the morphological and spectral properties of these objects. Thanks to these data, we discovered the second known X-shaped GRG, and a previously unidentified radio galaxy. Another object, observed both at kiloparsec (kpc) and pc scales, showed an extreme jet re-orientation of about 90 degrees. Given these intriguing premises, we embarked on a radio and X-ray follow-up to probe the lifecycle of these soft gamma-ray selected GRG. We found that more than half of these GRG have a nucleus with typical properties of young radio sources, while the remaining ones show a restarting radio morphology from low-frequency radio surveys or literature data. Among these, four are candidate hosts of a supermassive binary black hole system, and another two could host up to three distinct radio phases, underlying how the high-energy selection can pick up objects with peculiar accretion and radio properties.