Mass models and Sunyaev-Zeldovich effect predictions for a flux-limited sample of 22 nearby X-ray clusters

We define a 90% complete, volume-limited sample of 31 z < 0.1 X-ray cluster s and present a systematic analysis of public ROSAT PSPC data on 22 of thes e objects. Our efforts are undertaken in support of the Penn/OVRO Sunyaev-Z eldovich Effect (SZE) survey, and to this end we present predictions for th e inverse Compton optical depth toward all 22 of these clusters. We have pe rformed detailed Monte Carlo simulations in order to understand the effects of the cluster profile uncertainties on the SZE predictions given the OVRO 5.5 m telescope beam and switching patterns. We also present a similar ana lysis for the upcoming ACBAR experiment. For most of the clusters in the sa mple, we find less than a 5% uncertainty in the SZE predictions due to an i mperfect knowledge of the profile. A comparison of different cooling-flow m odeling strategies shows that our results are robust in this respect. The p rofile uncertainties are then one of the least significant components of ou r error budget for SZE-based distance measurements. The density models that result from this analysis also yield baryonic masses and, under the assump tion of hydrostatic equilibrium, total masses and baryon mass fractions. Ou r Monte Carlo profile analysis indicates that the baryon masses within 1 h( 100)(-1) Mpc for these clusters are accurate to better than similar to 5% a nd unaffected by realistic PSPC systematics. In the sample as a whole, we f ind a mean gas mass fraction of (7.02 +/- 0.28)h(100)(-3/2) x 10(-2) intern al to R-500 similar to 1 h(100)(-1) Mpc. This is in agreement with previous X-ray cluster analyses, which indicate an overabundance of baryons relativ e to the prediction of big bang nucleosynthesis for an Omega(M) = 1 univers e. Our analysis of the X-ray spectra confirms a previous claim of an excess absorbing column density toward A478, but we do not find evidence for anom alous column densities in the other 21 clusters. We also find some indicati ons of an excess of soft counts in the ROSAT PSPC data. A measurement of H- 0 using these models and OVRO SZE determinations; will be presented in a se cond paper.