Insights from Radio VLBI into the Central Engines of AGN feedback
How AGN inject energy into their surroundings affects their impact on their host galaxies. For the ~10%-20% of AGN which are “radio loud,” the interaction between the highly collimated relativistic jets emanating from closer to supermassive black hole (SMBH) and its surroundings are believed to result in “kinetic feedback” where gas is both head and pushed out of the galaxy, leading to a significant decrease in star formation rate. However, this process is far less understood for the 80% - 90% of AGN which are “radio quiet,” where both the origin of the radio emission and mode of AGN feedback are unknown. This talk will present the results derived from recent VLBI observations of a diverse sample of AGN – both quasars and lower-luminosity AGN associated with ionized gas outflows. We will then demonstrate how these observations allow us to distinguish between different possible origins for the observed radio emission, each associated with either “kinetic” or “thermal” feedback. Finally, we will present our initial findings which indicate that the origin of an AGN’s radio emission, and correspondingly the mode with which it affects its host galaxy, depends on its Eddington ratio.