Influence of dynemical radiative cooling on the local criterion of gravitational stability of selfgravitation gaseous disk

The results of a linear stability analysis of gaseous disk, in which heating and radiative cooling is dynamically important, we are presented. It is shown that cooling gives weak damping of acoustical modes and make more unstable gravity modes. So, the entropical-gravity mode is unstable for any wavelength and the local criterion of gravitational stability is absent. These effects may to influence on the mechanism of observational structure of gaseous disk in galaxies forming.
The physical cause of instability is phase shift between disturbances of internal energy and pressure on the one hand and disturbances of density on other hand, which uniquely determines by dispersion law. For acoustic modes all disturbances are in phase — increase of density leads to increase of internal energy; the wave behaves in the usual way. For the entropy modes disturbances of density are not in phase with disturbances of pressure and internal energy. So, local increase of density leads to decrease of pressure and internal energy. This is energetically favorable in accordance with the Le Chatelier — Brown principle and increases in time.