The galactic center dynamics

The innermost central part of the Galaxy has very complicated morphology and kinematics. We make an emphasis on the dynamical nature of the ‘mini-spiral’. Two cases are considered: (i) the putative black hole lies at the center of the dense stellar cluster and (ii) it is off the center. In the first case, the mechanism of the spiral arm generation can be over-reflection instability, and in the second case the axial asymmetry of the gravitational potential serves as a source of excitation of the density wave. In the both cases, the generated spiral density wave is consistent with the observed ‘mini-spiral’ if the upper limit to the black hole mass is ≅105M⊙.