Attenzione: a seguito delle disposizioni per il contenimento della diffusione del coronavirus, i seminari saranno in modalità online. Il link per il collegamento verrà reso disponibile nei giorni precedenti la data del seminario. Qui, invece, la playlist dei remote talks già messi in rete »
Estimating the lifetime of extragalactic magnetized hot cavities
Fabio del Sordo (Scuola Normale Superiore di Pisa)
Tuesday 27/10/2020 @ 14:00, Google Hangouts Meet
I will talk about some stability properties of buoyant cavities found in the intergalactic medium. These cavities have been observed to emanate in radio, x-and ?-rays from galactic disks in clusters of galaxies and similar structures, named Fermi Bubbles, have been observed also around our Galaxy. These structures are subject to shredding through MHD instabilities, especially the Kelvin-Helmholtz instability. I will present numerical models aimed at studying the evolution of these buoyant structures. I will show how the presence of a helical magnetic field inside these structures can make them significantly more stable than the non-magnetic structures. I will also discuss the possibility that non-helical magnetic fields harbour these cavities and show that in this case significantly stronger fields are required to stabilize them. One of the main conclusions reached by this investigation is that extragalactic cavities can be stable for longer than 100Myrs if they host helical magnetic fields.