Density Profiles of Dark Halos from their Mass Accretion Histories

Marcelo A. Alvarez; Kyungjin Ahn; Paul R. Shapiro

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arXiv · astro-ph/0302336

Density Profiles of Dark Halos from their Mass Accretion Histories

Marcelo A. Alvarez·Kyungjin Ahn·Paul R. Shapiro

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Abstract

We use the universal mass accretion history recently reported for simulations of halo formation in the cold dark matter model (CDM) to analyze the formation and growth of a single halo. We derive the time-dependent density profile three different ways, based upon three approximations of successively greater realism: equilibrium, radial orbits, and a fluid approximation. For the equilibrium model, the density profile is well-fit by either an NFW or Moore profile over a limited range of radii and scale factors. For the radial orbit model, we find profiles which are generally steeper than the NFW profile, with an inner logarithmic slope approaching -2, consistent with a purely radial collisionless system. In the fluid approximation, we find good agreement with the NFW and Moore profiles for radii resolved by N-body simulations (r/r_200 > 0.01), and an evolution of concentration parameter nearly identical to that found in N-body simulations. The evolving structure of cosmological halos is therefore best understood as the effect of a time-varying rate of mass infall on a smoothly distributed, isotropic, collisionless fluid.

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Marcelo A. Alvarez, Kyungjin Ahn, Paul R. Shapiro. 2003-02-17. Density Profiles of Dark Halos from their Mass Accretion Histories. https://arxiv.org/abs/astro-ph/0302336

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