forming pairs. The ratio of the marginal stability disk mass estimate to the total galaxy mass within four radial scalelengths remains within a range of 0.4—0.8. We see no evidence for a noticeable running of this ratio with either the morphological type or color index.

[**1.Introduction**]{}

The majority of stars in spiral and S0 galaxies are in general concentrated in old stellar disks with characteristic half-width of several hundreds parsecs. A formation and dynamical evolution of disks are the matter of hot debates, so the analysis of disk kinematical characteristics plays a key role (see e.g. Zasov, Sil’chenko (2010) and references therein). By kinematical characteristics we mean a rotation velocity and velocity dispersion of old stars, making up the bulk of stellar disk mass, as functions of radial coordinate in a disk plane. Typical velocity dispersion of old stellar disks equals to several dozens km/s. In general, it either can reflect the velocity of turbulent motion of gas which gave the birth to the first stellar generation, or can be the result of the dynamical heating of disk during its evolution.

Several possible mechanisms of equilibrium disk heating are known, the most effective are a scattering of stars on massive 