Spatial and velocity biases 447Figure 15.11.Density profiles for a cluster with mass 2. 5 × 1014 h−^1 M. Top panel:
Dark matter density in units of the mean matter density atz=0 (full curve) and atz= 1
(chain curve). The Navarro–Frenk–White profile (broken curve) provides a very good fit at
z=0. Thez=1 profile is given in proper (not comoving) units.Bottom panel: Number
density profiles of halos in the cluster atz=0 (full circles) and atz=1(opencircles)
compared with thez=0 dark matter profile (full curve). There is antibias on scales below
300 h−^1 kpc.
in the bottom panel). Note that, in the outer parts of the cluster, the halos closely
follow the dark matter.
15.3.4 Velocity bias
There are two statistics, which measure velocity biases—differences in velocities
of the galaxies (halos) and the dark matter. For a review of the results and