Summer Student Project: HI gas in the heart of 3C 84

© Claire Cook

The accretion of gas onto a central supermassive black hole can transform a quiet galactic center into one of the most energetic phenomena in the Universe—an Active Galactic Nucleus (AGN). AGN activity, i.e., the feeding and feedback processes, are believed to affect the evolution of galaxies. To better understand the exact mechanisms and spatial scales involved in these processes, we need detailed studies of the interaction between the AGN and the ambient gas. To do this, we use the Karl G. Jansky Very Large Array (JVLA), to analyze neutral atomic gas in the heart of the famous 3C 84 via the HI 21-cm absorption line at a spatial resolution of ~350pc. The HI absorption we detect is very broad (with a Full Width at Zero Intensity of ~1000km/s) and located only against 3C 84’s 14Jy-bright unresolved central radio component, with no other absorption seen against the jets or lobes. The broad velocity width of our absorption indicates that this centrally-located gas is highly turbulent, most likely due to AGN activity. Comparing the kinematics of our HI with that of molecular gas provides evidence that this HI is part of a fast rotating, 100-pc-scale circumnuclear disk located perpendicular to the radio jet axis, potentially serving as a fuel reservoir for the supermassive black hole. Overall, this is a fascinating and complex system where AGN fueling and feedback are occurring simultaneously.