The circumnuclear disk and ionized gas filaments as remnants of tidally   disrupted clouds
  Sticky particle calculations indicate that a coherent structure, a dispersion ring, forms when a cloud on a low angular momentum orbit passes close to the dynamical center of an isothermal sphere containing a central point mass. The cloud is tidally stretched and differentially wrapped, and dissipation in shocks organizes the gas into a precessing off-set elliptical ring which can persist for many rotation periods. The morphology and kinematics of the circumnuclear disk (CND) between 2 and 5 pc and the Northern arm in the inner 1 pc are well-represented by such structures. In the case of the Northern Arm, strong shocks which arise during the formation of the dispersion ring can lead to star formation even in the near tidal field of a massive black hole. 
R.H. Sanders (Kapteyn Astronomical Institute, Groningen, NL)