Massive black hole evolution in a normal galaxy nucleus

Tidal disruption and consumption of stars by massive black hole (BH) in the central stellar cluster of a normal galaxy nucleus leads to a fast growing of a BH on the stage of contraction of the stellar system. But subsequently the contraction of the system is replaced by its expansion owing to the heating by the stars which are gravitationally bounded with a BH. Growth of a BH on the stage of expansion is slowing down and its mass is finally freezed at the level of ∼ 106 Msun in the case of our Galaxy. Weak activity of such BH comes to an agreement with observations if the central stellar cluster consists mainly of a low mass stars and evolved compact stars like white dwarfs or neutron stars