Violent relaxation of ellipsoidal clouds

TL;DR

This study investigates how initial shape deviations in ellipsoidal, self-gravitating particle clouds influence violent relaxation, revealing their role in energy distribution, mass ejection, and formation of anisotropic structures.

Contribution

It demonstrates that initial deviations from spherical symmetry significantly affect the relaxation process and resulting structures, a novel insight into non-spherical gravitational systems.

Findings

Initial deviations control energy change and particle classification.

Mass and energy ejection lead to a $ ho(r) \\sim r^{-4}$ density profile.

Ejected particles form anisotropic shapes like bars and disks.

Abstract

An isolated, initially cold and ellipsoidal cloud of self-gravitating particles represents a relatively simple system to study the effects of the deviations from spherical symmetry in the mechanism of violent relaxation. Initial deviations from spherical symmetry are shown to play a dynamical role that is equivalent to that of density fluctuations in the case of an initially spherical cloud. Indeed, these deviations control the amount of particles energy change and thus determine the properties of the final energy distribution, particularly the appearance of two species of particles: bound and free. Ejection of mass and energy from the system together with the formation of a density profile decaying as $\rho(r) \sim r^{-4}$ and a Keplerian radial velocity dispersion profile, are the prominent features similar to those observed after the violent relaxation of spherical clouds. In addition, we find that ejected particles are characterized by highly non-spherical shapes, whose features can be traced in the initial deviations from spherical symmetry that are amplified during the dynamical evolution: particles can indeed form anisotropic configurations, like bars and/or disks, even though the initial cloud was very close to spherical.