Informazioni sull’evento


Coffee talks

Friday 05/02/2021 @ 11:30, On-line -

Marisa Brienza (University of Bologna / IRA-INAF), "A unique snapshot of the oldest AGN feedback phases"

Jetted Active Galactic Nuclei (AGN) inflate lobes of relativistic plasma and magnetic fields, which rise buoyantly as light ‘bubbles' into the intracluster medium (ICM) counterbalancing its spontaneous cooling. While the impact of jetted-AGN feedback is clear on energetic grounds, the exact physical mechanism that converts the bubble mechanical power into heat is not assessed yet. One way to investigate this aspect is through the study of radio bubbles at late stages of their evolution, when the plasma starts getting mixed with the ICM. However, up to now these have been very challenging to identify. Here I report the discovery of a spectacular group of galaxies showing radio emission extending up to hundreds of kpc-scales, with very complex, filamentary morphology. Our study of the system, based on LOFAR 53-MHz and 144-MHz observations combined with eRosita 0.5-2 keV observations, suggests that the radio emission is related to multiple episodes of the central AGN jet activity. Our results show that the bubble buoyancy power (equal to ~10^42 erg/s) canefficiently offset the radiative cooling of the ICM. Most interestingly though, we have detected for the first time at radio frequencies some very old AGN-driven bubbles, which have first transformed into toroidal (‘mushroom-shaped') structures - similar to what observed in M87 - and are now getting shredded into a multitude of filamentary substructures, likely under the influence of the group dynamics. This system clearly demonstrates how over timescales of hundreds of millions of years, the plasma released by the intermittent AGN-jet activity can disperse up to spatial scales of hundreds of kpc maintaining its integrity and without being completely mixed with the surrounding ICM.