On the Origin of the Inner Structure of Halos

Abstract

We calculate by means of the Press-Schechter formalism the density profile developed by dark-matter halos during accretion, i.e., the continuous aggregation of small clumps. We find that the shape of the predicted profile is similar to that shown by halos in high-resolution cosmological simulations. Furthermore, the mass-concentration relation is correctly reproduced at any redshift in all the hierarchical cosmologies analyzed, except for very large halo masses. The role of major mergers, which can cause the rearrangement of the halo structure through violent relaxation, is also investigated. We show that, as a result of the boundary conditions imposed by the matter continuously infalling into the halo during the violent relaxation process, the shape of the density profile emerging from major mergers is essentially identical to the shape the halo would have developed through pure accretion. This result explains why, according to high-resolution cosmological simulations, relaxed halos of a given mass have the same density profile regardless of whether they have had a recent merger or not, and why both spherical infall and hierarchical assembly lead to very similar density profiles. Finally, we demonstrate that the density profile of relaxed halos is not affected either by the capture of clumps of intermediate mass.

14 pages, 8 figures, accepted for publication in ApJ. Minor changes, matches the published version. To appear in the ApJ August 10, 2003 issue

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• Theoretical dark matter halo density profile
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• On the reliability of merger-trees and the mass growth histories of dark matter haloes
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• Scale Radii and Aggregation Histories of Dark Haloes
• Major Mergers of Haloes, Growth of Massive Black Holes and Evolving Luminosity Function of Quasars
• Alas, the dark matter structures were not that trivial
• The velocity anisotropy - density slope relation
• The flat density profiles of massive, and relaxed galaxy clusters
• Clues on Regularity in the Structure and Kinematics of Elliptical Galaxies from Self-consistent Hydrodynamical Simulations: the Dynamical Fundamental Plane
• The effects of Non-Gaussian initial conditions on the structure and substructure of Cold Dark Matter halos
• Violent and mild relaxation of an isolated self-gravitating uniform and spherical cloud of particles
• Culminating the peak CUSP to descry the dark side of halos
• Implications of Halo Inside-out Growth on the X-Ray Properties of Nearby Galaxy Systems within the Preheating Scenario
• Theoretical dark matter halo kinematics and triaxial shape
• A solution to the problems of cusps and rotation curves in dark matter halos in the cosmological standard model
• Testing DARKexp against energy and density distributions of Millennium-II halos
• The spherical collapse model with shell crossing
• Extended Press-Schechter theory and the density profiles of dark matter haloes
• Modelling the dynamical friction timescale of sinking satellite
• Nature and Nurture in Dark Matter Halos
• Accurate Analytic Mass-Scale Relations for Dark Matter Haloes of all Masses and Redshifts
• Statistical Mechanics of Collisionless Orbits. V. The approach to equilibrium for idealized self-gravitating systems
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• Dark Matter Angular Momentum Profile from the Jeans Equation
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