A HYBRID N-BODY CELLULAR AUTOMATON SCHEME FOR MODELING PROPAGATING STAR-FORMATION IN GALAXIES/

We present a numerical scheme for modelling star formation in galaxies based on the dual operation of gravitational instabilities and propag ating star formation. Star formation is superposed on a mechanical N-b ody simulation of a collisional particle system by using a cellular au tomaton framework. The simulations involve 5000 particles representing gas clouds which can collide inelastically, and have been performed o n a 2D square surface with quasiperiodic boundary conditions. The inpu t of kinetic energy from star-forming regions leads to self-regulation of the global dynamics of star formation. The model naturally generat es cloud complexes assembled from groups of cloud particles and simula tes the ignition and propagation of star formation in such complexes l eading to the formation of low density bubbles and expanding shells. T he percentage of the model surface undergoing star formation and the r atio of the rates of stimulated to spontaneous star formation are show n to be consistent with models based on the theory of Stochastic Self- Propagating Star Formation (SSPSF). The code is shown to lead to star formation that propagates very nearly isotropically and can thus be ad apted to the case of rotating disc galaxies without geometrical modifi cation.