Impulsive gas fueling to the galactic center in a barred galaxy due to falls of gas clouds.

This article focuses on numerical simulations investigating gas dynamics and evolution in the central regions of barred galaxies, particularly the formation and behavior of gas clouds within the x-2 orbital ring. The simulations demonstrate that as a stellar bar grows, it induces an oval-shaped x-2 gas ring within about 1 kpc, which becomes self-gravitationally unstable, leading to fragmentation into gas clouds. Cloud–cloud collisions and energy injections from Type II supernovae cause some clouds to deviate from the ring, lose angular momentum through repeated collisions near their apocenters, and eventually fall into the galactic center, resulting in episodic gas fueling. This mechanism is proposed to play a significant role in galactic nuclear evolution, including active galactic nucleus (AGN) activity, supermassive black hole growth, and nuclear starbursts. The study's results align with observations of molecular clouds in barred galaxies such as M 83 and highlight the importance of self-gravity and multi-phase interstellar medium modeling in understanding central gas dynamics.