THE CIRCUMNUCLEAR MATERIAL IN THE GALACTIC-CENTER - A CLUE TO THE ACCRETION PROCESS

On the basis of 'sticky particle' calculations, it is argued that the gas features observed within 10 pc of the Galactic Centre - the circum nuclear disc (CND) and the ionized gas filaments - as well as the newl y formed stars in the inner 1 pc can be understood in terms of tidal c apture and disruption of gas clouds on low angular momentum orbits in a potential containing a point mass. The calculations demonstrate that a dissipative component forms a 'dispersion ring', an asymmetric elli ptical torus precessing counter to the direction of rotation, and that this shape can be maintained for many orbital periods. For a range of plausible initial conditions, such a structure can explain the morpho logy and kinematics of the CND and of the most conspicuous ionized fil ament. While forming the dispersion ring, a small cloud with low speci fic angular momentum is drawn into a long filament which repeatedly co llides with itself at high velocity. The compression in strong shocks is likely to lead to star formation even in the near tidal field of th e point mass. This process may have general relevance to accretion on to massive black holes in normal and active galactic nuclei.