Generation of spiral density waves by bars in differentially rotating disks

The generation of spiral density waves by a bar gravitational field in differentially rotating flat galaxy subsystems is considered. Dynamics of flat galaxy subsystem is described by a set of hydrodynamics equations. Nonstationary nonlinear response of differentially rotating gaseous disk by potential of a bar having form of an ellipsoid for different values of its angular velocity is numerically investigated.The generation of large-scale trailing spiral pattern takes place if the bar leads to the rotation of most parts of the disk. The natural feature of large-scale patterns is the appearence of ring like structures. The quasistationary wave pattern is established for sufficiently slow inclusion of bar potential. The peaks of gas density appears on the leading edges of bar