The velocity dispersion profiles of the galaxies are also measured using a
method faithful to current observational techniques. A slit 3.2 kpc in
width
is laid along the apparent major axis in three independent directions.
This corresponds observationally to a 1.5 arcsecond slit laid across a
galaxy at a distance of 100 Mpc.
Particles are binned in squares 3.2 kpc on a side and the mean line-of-sight
velocity and velocity dispersion is measured in each bin.
Like real ellipticals,
the galaxy rotates slowly about its minor axis
with 
km/s (Franx, Illingworth & Heckman 1989)[24].
Figure 9
shows the velocity dispersion profile along the apparent major
axis for the three lines of sight down each of the principal axes.
Figure 9: Velocity dispersion profile measured along a slit laid on the
major axis for the three principal axis projections of the galaxy.
The velocity dispersion
declines slowly with distance from the centre. There is no sign of an
upturn at large distances.
The central value peaks between 300 and 450 km/s depending on the line of sight. The large value of 450 km/s occurs when looking exactly down the long axis of the galaxy showing the anisotropy of the velocity ellipsoid in this flattened triaxial stellar system. These central values again are in accord with real giant ellipticals although the value of 450 km/s might be considered too large (Fisher et al. 1995)[23]. The velocity dispersion only declines gradually out to 60 kpc (about 3 effective radii) again in similar fashion too many elliptical galaxies. There is no sign of an upturn in the velocity dispersion at large radii as seen in the exceptional case of the cD galaxy in A2029 (Dressler 1979)[17].
In three dimensions, the measured velocity dispersion is nearly isotropic to the
centre but becomes radial anisotropic with a radial anisotropy
parameter (Binney & Tremaine 1987)[8],
at 3 
.
The density profiles of Figure 7 for
the dark matter and stars were fit with Hernquist
(1990) models and used to solve the spherical Jeans
equations for the velocity dispersion profile of the stars
using constant values for the anisotropy parameter, 
.
Figure 10 shows that the velocity profile is consistent with
the mass model for values of 
within r < 20 kpc (
).
The best fit spherical Jeans model in Figure 10 is one
where the anisotropy grows monotonically from the center with 
to at 3 .
Figure 10: The spherically averaged radial velocity dispersion profile compared
to anisotropic spherical model predictions from the fitted density profile.
Each line is labelled with the anisotropy parameter used in the model.
The anisotropy of the model rises from about 0.2 in the center to 0.5 at
100 kpc (
). The dashed line represents a best fit model with 
growing monotonically from 0.0 to 0.5 from the center to 100 kpc.