Dark halo mergers and the formation of a universal profile |
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| Authors: | Syer & Simon D M White |
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| Institution: | Max-Planck-Institut für Astrophysik, 85740 Garching-bei-München, Germany |
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| Abstract: | We argue that a universal density profile for dark matter haloes arises as a natural consequence of hierarchical structure formation: it is a fixed point in the process of repeated mergers. We present analytic and numerical arguments for the emergence of a particular form of the central cusp profile. At small radii, the density should vary as r ?α, with α determined by the way in which the characteristic density of haloes scales with their mass. If small haloes are dense, then α is large. The mass–density relation can be related to the power spectrum of initial fluctuations, P ( k ), through 'formation time' arguments. Early structure formation leads to steep cusps. For P ( k ) ～ k n we find α ? 3(3 + n )/(5 + n ). The universal profile is generated by tidal stripping of small haloes as they merge with larger objects. |
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| Keywords: | celestial mechanics stellar dynamics galaxies: kinematics and dynamics cosmology: theory dark matter |
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