Dissipationless galaxy formation from nonisolated density perturbations
Abstract
The nondissipative evolution of an aspherical initially small density perturbation and the collapse of the resulting bound object (protogalaxy) is studied numerically by the nbody method. The investigation is based on an improved version of the model proposed by Yoglis & Hiotelis (1989). This model is based on Aasheth's nbody code and takes into account the dynamical effects on the evolution of the protogalaxy of both the close neighbouring material and the extensive mass environment. The results show that the final radial profile of the density can be appreciably different from the prediction of the similarity solution. The difference is due to the redistribution of binding energies among the particles after the collapse, and to the asphericity of the initial density profile. The collapse factor of the various shells is found to depend on the final radius r as r^β^, with β ~0.5. The angular momentum the protogalaxy acquires in the tidal field of its environment is discussed. The values of the spin parameter λ and their distribution versus the cumulative mass from the center of the protogalaxy are also examined. In some cases the inner parts of the protogalaxy counterrotate with respect to the outer shells.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 September 1991
 Bibcode:
 1991A&A...249....5V
 Keywords:

 Galactic Evolution;
 Galactic Nuclei;
 Particle Energy;
 Perturbation Theory;
 Density Distribution;
 Energy Dissipation;
 Energy Distribution;
 Universe;
 Astrophysics