Universal properties of violently relaxed gravitational structures

Abstract

We study the collapse and virialization of an isolated spherical cloud of self-gravitating particles initially at rest and characterised by a power-law density profile, with exponent 0<= α< 3, or by a Plummer, an Hernquist, a NFW, a Gaussian profile. We find that in all cases the virialized structure formed after the collapse has a density profile decaying, at large enough radii, as ~ r^{-4}, and a radial velocity dispersion profile decaying as ~r^{-1}. We show that these profiles originate from the physical mechanism responsible of the ejection of a fraction of cloud's mass and energy during the collapse and that this same mechanism washes out the dependence on the initial conditions. When a large enough initial velocity dispersion is given to the cloud particles, ejection does not occur anymore and consequently the virialized halo density and velocity profiles display features which reflect the initial conditions.

8 pages, 7 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal

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• Particle ejection during mergers of dark matter halos
• Symplectic coarse graining approach to the dynamics of spherical self-gravitating systems
• Formation of disks with long-lived spiral arms from violent gravitational dynamics
• A toy model to test the accuracy of cosmological N-body simulations
• Angular momentum generation in cold gravitational collapse
• Properties of self-gravitating quasi-stationary states
• Formation of satellites from cold collapse
• Limitation of symmetry breaking by gravitational collapse: the revisit of Lin-Mestel-Shu instability
• Formation of spiral structure from the violent relaxation of self-gravitating disks
• Gravitational collapse from cold uniform asymmetric initial conditions