Cellular Automaton experiments on local galactic structure. II. Numerical simulations

¹ Institut de Physique, Sart–Tilman, B–4000, Liège, Belgium
² Institute of Astronomy, Madingley Road, Cambridge CB3 OHA, UK, and Institut d'Astrophysique, 5, Avenue de Cointe, B–4000 Liège, Belgium

Send offprint request to: A. Lejeune

Received: 27 October 1994
Accepted: 6 March 1996

Abstract

This paper is a step towards demonstrating that the multi–parameter Cellular Automaton framework designed for the simulation of local galactic structure, developed in a companion paper (Perdang & Lejeune 1996, Paper I), is capable of duplicating the local irregularities observed in the structure of flocculent spiral galaxies. The numerical simulations exhibit the development of fractured galactic arms and the formation of fractal geometries associated with the matter distribution (fractal structure of the arms, of bulk dimension ≈ 1.7 and border dimension ≈ 1.3; distribution of different stellar components on fractal supports, of dimension ≈ 1.6, for reasonable estimates of the free model parameters). The prediction of fractional values for the different dimensions specifying the simulated structures can be exploited as a qualitative test of adequacy of the proposed model. The precise quantitative values of the observed dimensions, in conjunction with the observable global mass fractions of the different galactic components, play the parts of constraints for the free model parameters. We show that the currently theoretically inaccessible values of the free parameters of the formulation can be recovered from observation.