  We investigate a hypothesis regarding the origin of the scalelength in halos
formed in cosmological N-body simulations. This hypothesis can be viewed as an
extension of an earlier idea put forth by Merritt and Aguilar. Our findings
suggest that a phenomenon related to the radial orbit instability is present in
such halos and is responsible for density profile shapes. This instability sets
a scalelength at which the velocity dispersion distribution changes rapidly
from isotropic to radially anisotropic. This scalelength is reflected in the
density distribution as the radius at which the density profile changes slope.
We have tested the idea that radially dependent velocity dispersion anisotropy
leads to a break in density profile shape by manipulating the input of a
semi-analytic model to imitate the velocity structure imposed by the radial
orbit instability. Without such manipulation, halos formed are approximated by
single power-law density profiles and isotropic velocity distributions. Halos
formed with altered inputs display density distributions featuring scalelengths
and anisotropy profiles similar to those seen in cosmological N-body
simulations.
