Tidally-Controlled Fragmentation around Black Holes, Massive Clumps, Protostars, and the Galactic Center

Abstract

Gravity plays important roles at multiple scales in the universe. An important, yet often neglected, role of gravity is its ability in driving anisotropic fragmentation through tides. When tides dominate, fragmentation becomes anisotropic, and the Jeans length along the short axis, $l_{\rm tidal, Jeans}$, is approximately $\sigma_{\rm v}/\sqrt{G \rho_{\rm mean}}$, determined by the external tides through the mean density $\rho_{\rm mean}$. We compare predictions of $l_{\rm tidal, Jeans}$ against observational results in massive star-forming clumps, the Circumnuclear Disk (CND) around the supermassive black hole Sgr A* at the center of the Galaxy, the Central Molecular Zone in the Galactic Center, a hub-filament system, and a streamer around a young star. We find that the observed widths of these filamentary structures match theoretical predictions from tidally-controlled Jeans fragmentation. The formation of filaments can potentially shield cold gas against radiation pressure and photoevaporation, as well as hydrodynamical interaction with the ambient medium, potentially enabling the cold gas to survive. Thus, tidal forces are major players regulating gas transport around massive objects.