Skip to main content

Research Repository

Advanced Search

The inner structure of ACDM haloes - III. Universality and asymptotic slopes

Navarro, J.F.; Hayashi, E.; Power, C.; Jenkins, A.R.; Frenk, C.S.; White, S.D.M.; Springel, V.; Stade, J.; Quinn, T.R.

The inner structure of ACDM haloes - III. Universality and asymptotic slopes Thumbnail


J.F. Navarro

E. Hayashi

C. Power

S.D.M. White

V. Springel

J. Stade

T.R. Quinn


We investigate the mass profile of cold dark matter (ΛCDM) haloes using a suite of numerical simulations spanning five decades in halo mass, from dwarf galaxies to rich galaxy clusters. These haloes typically have a few million particles within the virial radius (r200), allowing robust mass profile estimates down to radii <1 per cent of r200. Our analysis confirms the proposal of Navarro, Frenk & White (NFW) that the shape of the ΛCDM halo mass profiles differs strongly from a power law and depends little on mass. The logarithmic slope of the spherically averaged density profile, as measured by β=−d ln ρ/d ln r, decreases monotonically towards the centre and becomes shallower than isothermal (β< 2) inside a characteristic radius, r2. The fitting formula proposed by NFW provides a reasonably good approximation to the density and circular velocity profiles of individual haloes; circular velocities typically deviate from NFW best fits by <10 per cent over the radial range that is numerically well resolved. Alternatively, systematic deviations from the NFW best fits are also noticeable. Inside r2, the profile of simulated haloes becomes shallower with radius more gradually than predicted and, as a result, NFW fits tend to underestimate the dark matter density in these regions. This discrepancy has been interpreted as indicating a steeply divergent cusp with asymptotic inner slope, β0≡β(r = 0) 1.5. Our results suggest a different interpretation. We use the density and enclosed mass at our innermost resolved radii to place strong constraints on β0: density cusps as steep as r1.5 are inconsistent with most of our simulations, although β0= 1 is still consistent with our data. Our density profiles show no sign of converging to a well-defined asymptotic inner power law. We propose a simple formula that reproduces the radial dependence of the slope better than the NFW profile, and so may minimize errors when extrapolating our results inward to radii not yet reliably probed by numerical simulations.


Navarro, J., Hayashi, E., Power, C., Jenkins, A., Frenk, C., White, S., …Quinn, T. (2004). The inner structure of ACDM haloes - III. Universality and asymptotic slopes. Monthly Notices of the Royal Astronomical Society, 349(3), 1039-1051.

Journal Article Type Article
Acceptance Date Dec 29, 2003
Online Publication Date Apr 11, 2004
Publication Date Apr 11, 2004
Deposit Date Jul 16, 2007
Publicly Available Date Aug 11, 2014
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 349
Issue 3
Pages 1039-1051
Keywords Gravitation, Cosmology, Theory, Dark matter, Halos, Surface brightness galaxies, Density profiles, Rotation curves, Power spectrum, Dependence, Models, Constraints, Evolution, Mass.


Published Journal Article (679 Kb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2004 The Authors Published on behalf of Royal Astronomical Society. All rights reserved.

You might also like

Downloadable Citations