We demonstrate that the “ sub-keplerian ” rotation curve of maser spots in NGC 1068 can be explained by the gravitational attraction of the disc orbiting the central black hole .
Possible parameters matching observations are : black hole mass \simeq ( 1.2 \pm 0.1 ) \times 10 ^ { 7 } M _ { \odot } , disc outer edge \gtrsim 1.3 pc , aspect ratio 3 \times 10 ^ { -3 } \lesssim \frac { H } { R } \lesssim 0.3 , surface density \Sigma \propto R ^ { -1.05 \pm 0.10 } , and disc mass \simeq ( 9.4 \pm 1.6 ) \times 10 ^ { 6 } M _ { \odot } .
The physical conditions required for the excitation of masers are fulfilled , and the outer disc would stand in a gravitationally marginally stable state .