Secular evolution of spiral galaxies. II. Formation of quasi-stationary spiral modes

摘要

In this second of a series of three papers, we demonstrate that the kind of spiral patterns in disk galaxies which can remain quais-stationary on the timescale of a Hubble time are spontaneously formed spiral modes. The amplitude of the spiral mode is limited to a finite value, determined by the basic state characteristics, through a collective dissipation process, introduced in Paper I of this series. We show that the radial distribution of the total torque coupling integral of a spontaneously formed Spiral mode must be(and is found to be) of a characteristic bell shape, with the peak of the bell located At the corotation radius of the mode.