Physics of the Multiphase Structure of Ultrafast Outflows from AGN

AGN outflows provide a natural link between a galaxy and its central black hole. These outflows are not smooth, not even the fastest ones, the so-called ultrafast outflows (UFOs). In the past, we showed that it is possible to explain the multiphase structure of slower thermally driven outflows using the theory of a thermally unstable plasma. However, it has been challenging to account for the multiphase structure of UFOs using the same theory. Here, we present physical arguments and supportive numerical simulations for why clumps can form in an already fully accelerated outflow. We also contrast this explanation with an alternative scenario in which clumps form prior to being accelerated.