Vaulting the barrier: An intrinsic mechanism to fuel the gas beyond the nuclear ring into the central region of barred galaxies

Vaulting the barrier: An intrinsic mechanism to fuel the gas beyond the nuclear ring into the central region of barred galaxies
Kotaro Kobayashi, Naomichi Yutani, Takayuki R. Saitoh, Junichi Baba, Keiichi Wada
arXiv:2604.17955v2 Announce Type: replace
Abstract: Gas delivery to galactic centers powers nuclear starbursts and active galactic nuclei (AGNs), yet bar-driven inflow is generally expected to stall in a nuclear ring a few hundred parsecs across. Using three-dimensional Lagrangian hydrodynamic simulations in a fixed barred potential, we identify a bypass channel in which a fraction of the inflowing gas acquires vertical momentum, vaults across the ring, and reaches the inner few tens of parsecs. This pathway is absent in two-dimensional calculations, which instead predict long-lived stagnation at the ring. We find that the circumnuclear material within $sim 50$ pc originates from gas initially located outside the ring ($gtrsim 300$ pc), rather than from secondary inflow out of the ring itself. Successful delivery requires both a sufficiently large vertical excursion, $|z| sim 100$ pc before encountering the ring, and substantial loss of azimuthal angular momentum $L_z$. The resulting inflow is organized rather than chaotic: center-reaching trajectories are confined to a limited spatial region set by the scale height of the ring gas. Most bar-driven gas still accumulates near the resonance and fuels star formation in the nuclear ring, but the vaulting stream selects a modest yet sufficient fraction that penetrates to the circumnuclear disk. These results suggest that intrinsically three-dimensional gas motions help link nuclear starbursts, AGN fueling, and the frequent misalignment of nuclear disks with respect to their host galaxies.arXiv:2604.17955v2 Announce Type: replace
Abstract: Gas delivery to galactic centers powers nuclear starbursts and active galactic nuclei (AGNs), yet bar-driven inflow is generally expected to stall in a nuclear ring a few hundred parsecs across. Using three-dimensional Lagrangian hydrodynamic simulations in a fixed barred potential, we identify a bypass channel in which a fraction of the inflowing gas acquires vertical momentum, vaults across the ring, and reaches the inner few tens of parsecs. This pathway is absent in two-dimensional calculations, which instead predict long-lived stagnation at the ring. We find that the circumnuclear material within $sim 50$ pc originates from gas initially located outside the ring ($gtrsim 300$ pc), rather than from secondary inflow out of the ring itself. Successful delivery requires both a sufficiently large vertical excursion, $|z| sim 100$ pc before encountering the ring, and substantial loss of azimuthal angular momentum $L_z$. The resulting inflow is organized rather than chaotic: center-reaching trajectories are confined to a limited spatial region set by the scale height of the ring gas. Most bar-driven gas still accumulates near the resonance and fuels star formation in the nuclear ring, but the vaulting stream selects a modest yet sufficient fraction that penetrates to the circumnuclear disk. These results suggest that intrinsically three-dimensional gas motions help link nuclear starbursts, AGN fueling, and the frequent misalignment of nuclear disks with respect to their host galaxies.