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A universal density slope – velocity anisotropy relation

Published online by Cambridge University Press:  19 May 2006

G.A. Mamon ,
F. Combes ,
C. Deffayet ,
B. Fort ,
S.H. Hansen ,
B. Moore  and
J. Stadel
S.H. Hansen
Affiliation:
University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
B. Moore
Affiliation:
University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
J. Stadel
Affiliation:
University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Abstract

One can solve the Jeans equation analytically forequilibrated dark matter structures, once given two pieces of inputfrom numerical simulations. These inputs are 1) a connection betweenphase-space density and radius, and 2) a connection between velocityanisotropy and density slope, the α – β relation. The first(phase-space density vs. radius) has been analysed through severaldifferent simulations, however the second (α – β relation) has notbeen quantified yet. We perform a large set of numerical experimentsin order to quantify the slope and zero-point of the α – βrelation. This allows us to conclude that equilibrated dark matterstructures indeed have zero central velocity anisotropy,central densityslope of α0 ≈ –0.8, and outer anisotropy ofapproximately β∞ ≈ 0.5.

Type
Research Article
Information
European Astronomical Society Publications Series , Volume 20: Mass Profiles and Shapes of Cosmological Structures , 2006 , pp. 33 - 36
Copyright
© EAS, EDP Sciences, 2006

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