The stability of the Circumnuclear Disk clouds in the Galactic Centre

The influence of rotation and magnetic fields on the physical properties of isothermal gas clouds is discussed. The presence of rotation and/or magnet ic fields results in an increase of the critical cloud mass with respect to gravitational instability for clouds of a given temperature and external p ressure. Rotating clouds have higher densities. Consequently, they are more stable against tidal shear than non-rotating clouds. They can approach the Galactic Centre up to a radius of similar to2 pc without being disrupted b y the tidal shear due to the gravitational potential. For smaller radii the clouds either collapse or become tidally disrupted. We suggest that this m echanism is responsible for the formation of the inner edge of the Circumnu clear Disk in the Galactic Centre.