ar X iv : a st ro - p h / 05 10 65 6 v 1 2 1 O ct 2 00 5 The velocity anisotropy - density slope relation Steen
نویسنده
چکیده
One can solve the Jeans equation analytically for equilibrated dark matter structures, once given two pieces of input from numerical simulations. These inputs are 1) a connection between phase-space density and radius, and 2) a connection between velocity anisotropy and density slope, the α − β relation. The first (phase-space density v.s. radius) has already been analysed through several different simulations, however the second (α− β relation) has not been quantified yet. We perform a large set of numerical experiments in order to quantify the slope and zero-point of the α− β relation. We find strong indication that the relation is indeed an attractor. When combined with the assumption of phase-space being a power-law in radius, this allows us to conclude that equilibrated dark matter structures indeed have zero central velocity anisotropy β0 ≈ 0, central density slope of α0 ≈ −0.8, and outer anisotropy of β∞ ≈ 0.5.
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