  The recently revised cosmological constraints from the Five-Year WMAP data
ameliorate previous tension between cosmological constraints from the microwave
background and from cluster abundances. We demonstrate that the revised
estimates of cosmological parameters are in excellent agreement with the mass
function of X-ray clusters in the Sloan Digital Sky Survey. Velocity
segregation between galaxies and the underlying dark matter could cause virial
mass estimates to be biased, causing the mass scale of the mass function to be
offset from the true value. Modest velocity segregation
($\sigma_{gxy}/\sigma_{DM}$=1.13$^{+0.06}_{-0.05}$) is sufficient to match the
mass function to the Five-Year WMAP results. When the new WMAP results are
combined with constraints from supernovae and baryon acoustic oscillations,
there is no need for velocity segregation
($\sigma_{gxy}/\sigma_{DM}$=1.05$\pm$0.05). This result agrees with
expectations for velocity segregation from state-of-the-art numerical
simulations of clusters. Together with the improved agreement between the new
WMAP results and recent cosmic shear measurements, this result demonstrates
that the amplitude of large-scale structure in the nearby universe matches that
predicted from the structure seen in the microwave background. The new
constraint we place on velocity segregation in clusters indicates that virial
mass estimates for clusters are reasonably accurate. This result suggests that
future cluster surveys will be able to probe both cosmological parameters and
fundamental cluster physics.

Astrophysics