![]() ![]() © CAMBRIDGE UNIVERSITY PRESS 1999
| |
2.9. Velocity Dispersion
The typical radial (line-of-sight) velocity dispersion of galaxies in rich clusters (median value) is
![]() | (22) |
The typical range of radial velocity dispersion in rich clusters (Struble and Rood 1991) is
![]() | (23) |
A weak correlation between
r and
richness exists; richer
clusters exhibit, on average, larger velocity dispersion
(Bahcall 1981).
The observed velocity dispersion of galaxies in rich clusters is
generally consistent with the velocity implied by the X-ray
temperature of the hot intracluster gas
(Section 3.5), as well as
with the cluster velocity dispersion implied from observations of
gravitational lensing by clusters (except possibly in the central
core). Velocity dispersion and temperature profiles as a function of
distance from the cluster center have been measured only for a
small number of clusters so far. The profiles are typically isothermal
[
2r(r) ~
Tx(r) ~ constant] for
r
0.5-1h-1 Mpc, and drop somewhat at larger distances.