Gravitational instability of perturbations in a background nonlinear nonstationary model of a disk-like system. II. Large-scale tesseral oscillation modes

Abstract

We study the gravitational instability of large-scale tesseral perturbation modes against the background of the previously built model od a disk galaxy, nonlinearly pulsating and anisotropic in velocities. This model rests on a nonstationary generalization of the well-known equilibrium isotropic disk model due to Bisnovaty-Kogan and Zeldovich. We have obtained the corresponding nonstationary analogs of the dispersion equations for the five basic tesseral perturbation modes. The results are presented in the form of critical dependences of the initial virial ratio on the superposition parameter for different degrees of rotation. We have also carried out a comparative analysis of the instability increments for all large-scale perturbation modes.