Initial evolutionary stages for the gaseous disk of the constructed disk galaxy model (axisymmetric isothermal case). The evolution of the model was calculated including a live halo and stellar disk. The upper snapshots show the disk views face-on for times 0, 0.1, 0.2, 0.3 and 0.4; the grey intensities correspond to the logarithm of the surface density. The bottom panels show the dependence of various disk quantities on the cylindrical radius R at the same times. Here Σ_g is the surface density of the gas; z_1/2 is the median of the |z| value, i.e a measure of the disk thickness (see Sotnikova & Rodionov 2006) and is the mean tangential velocity.