The intracluster gas fraction in X-ray clusters: constraints on the clustered mass density

The mean intracluster gas fraction of X-ray clusters within their hydrostatic regions is derived from recent observational compilations of David, Jones & Forman and White & Fabian. At radii encompassing a mean density 500 times the critical value, the individual sample bi-weight means are moderately ($2.4 by numerical simulations removes the discrepancy and results in a combined sample mean and standard error $\(r₅₀₀) = (0.060 \± 0.003) assumption to maximize cluster gas content, this value constrains the universal ratio of total, clustered to baryonic mass \Ωₘ/\Ωb \≤ 23.1 physically plausible approach based on low D/H inferences from quasar absorption spectra and accounting for baryons within cluster galaxies yields an estimateØmega_m \2/3 = 0.28 \± 0.07$ with sources of systematic error involved in the derivation providing approximately $35%$ uncertainty. Additional effects which could provide consistency with the Einstein-deSitter case $Ømega_m \ 1$ are presented, and their observable signatures discussed.