The Impact of Feedback-driven Outflows on Bar Formation

We investigate the coupling between the temporal variation from central mass outflows and the bar instability. We show that gravitational fluctuations from AGN-driven mass outflows affect the radial motion of disk orbits. The resulting incoherence in orbital phase leads to the disruption of the bar-forming dynamics. Bar formation is suppressed in galaxies with repeated outflow events in the range 10 Myr to 200 Myr with wind mass ~15% of the disk within ~0.5 scale lengths or 1.4% of the total disk mass. The work done by central AGN feedback is capable of reducing the amplitude or, with enough amplitude, destroying an existing bar. Conversely, SF feedback that is distributed across the disk has insufficient spatial and temporal coherence to suppress bar formation.

To model the dynamics of the coupling and interpret the results of the full N-body simulations, we introduce a generalization of the Hamiltonian mean-field (HMF) model, drawing inspiration from the Lynden-Bell (1979) mechanism for bar growth. Our non-linear \emph{BarHMF} model is designed to reproduce linear perturbation theory in the low-amplitude limit. Without feedback, this model exhibits exponential growth whose rate depends on disk mass and reproduces the expected saturation of bar growth observed in N-body simulations. We describe several promising applications of the BarHMF model beyond this study.