Chandra Evidence for AGN Feedback in the Spiral Galaxy NGC 6764

Abstract

We report the Chandra detection of X-ray emission spatially coincident with the kiloparsec-scale radio bubbles in the nearby (DL ~ 31 Mpc) AGN-starburst galaxy NGC 6764. The X-ray emission originates in hot gas (kT ~ 0.75 keV), which may either be contained within the radio bubbles, or in a shell of hot gas surrounding them. We consider three models for the origin of the hot gas: (1) a starburst-driven galactic wind, (2) shocked gas associated with the expanding radio bubbles, and (3) gas heated and entrained into the bubbles by jet/ISM interactions in the inner AGN outflow. We rule out a galactic wind based on significant differences from known galactic wind systems. The tight correspondence between the brightest X-ray emission and the radio emission in the inner outflow from the Seyfert nucleus, as well as a correlation between X-ray and radio spectral features suggestive of shocks and particle acceleration, lead us to favor the third model; however, we cannot firmly rule out a model in which the bubbles are driving large-scale shocks into the galaxy ISM. In either AGN-driven heating scenario, the total energy stored in the hot gas is high, ~1056 ergs, comparable to the energetic impact of low-power radio galaxies such as Centaurus A, and will have a dramatic impact on the galaxy and its surroundings