Lumpy structures in self-gravitating disks

Following Toomre & Kalnajs (1991), local models of slightly dissipative sel f-gravitating disks show how inhomogeneous structures can be maintained ove r several galaxy rotations. Their basic physical ingredients are self-gravi ty, dissipation and differential rotation. In order to explore the structur es resulting from these processes on the kpc scale, local simulations of se lf-gravitating disks are performed in this paper in 2D as well as in 3D. Th e third dimension becomes a priori important as soon as matter clumping cau ses a tight coupling of the 3D equations of motion. The physically simple a nd general framework of the model permits to make conclusions beyond the he re considered scales. A time dependent affine coordinate system is used, al lowing to calculate the gravitational forces via a particle-mesh FFT-method , increasing the performance with respect to previous direct force calculat ions. Persistent patterns, formed by transient structures, whose intensity and morphological characteristic depend on the dissipation rate are obtaine d and described. Some of our simulations reveal first signs of mass-size an d velocity dispersion-size power-law relations, but a clear scale invariant behavior will require more powerful computer techniques.