``Galaxy Cluster Baryon Fractions, Cluster Surveys and Cosmology''

Abstract
The properties of nearby galaxy clusters
limit the range of cosmological parameters consistent with our
universe. We describe the limits which arise from studies of the
intracluster medium (ICM) mass fraction fICM and consideration of the
possible sources of systematic error: Omega_M<0.44h_{50}^{1/2}
at 95% confidence. We emphasize that independent of Type Ia
supernovae (SNe Ia) observations, this cluster study, taken
together with published cosmic microwave background (CMB) anisotropy
studies, indicates a nonzero
quintessence or dark energy component Omega_Q>0.
We then discuss future galaxy cluster
surveys which will probe the abundance of galaxy clusters to
intermediate and high redshift.
We investigate the sensitivity of these surveys to the cosmological
density parameter Omega_M and the equation of state parameter
w of any quintessence component. In particular, we show that
cluster survey constraints from a proposed large solid angle Xray
survey are comparable in precision and complementary in nature
to constraints expected from future CMB anisotropy and SNe Ia studies.

