Nonnucleosynthetic Constraints on the Baryon Density and Other Cosmological Parameters

Because the baryon-to-photon ratio eta_{10} is in some doubt, we dropnucleosynthetic constraints on eta_{10} and fit the three cosmologicalparameters (h, Omega_M, eta_{10}) to four observational constraints: Hubbleparameter h_o = 0.70+-0.15, age of the universe t_o = 14+7-2 Gyr, cluster gasfraction f_o \equiv f_G h^{3/2} = 0.060 +- 0.006, and effective shape parameterGamma_o = 0.255 +- 0.017. Errors quoted are 1 sigma, and we assume Gaussianstatistics. We experiment with a fifth constraint Omega_o = 0.2 +- 0.1 fromclusters. We set the tilt parameter n = 1 and the gas enhancement factorUpsilon = 0.9. We consider CDM models (open and Omega_M = 1) and flat LambdaCDMmodels. We test goodness of fit and draw confidence regions by the Delta chi^2method. CDM models with Omega_M = 1 (SCDM models) are accepted only because thelarge error on h_o allows h < 0.5. Baryonic matter plays a significant role inGamma_o when Omega_M \sim 1. Open CDM models are accepted only for Omega_M\gtrsim 0.4. The combination of the four other constraints with Omega_o = 0.2+- 0.1 is rejected in CDM models with 98% confidence, suggesting that light maynot trace mass. LambdaCDM models give similar results. In all of these models,eta_{10} \gtrsim 6 is favored strongly over eta_{10} \lesssim 2. This suggeststhat reports of low deuterium abundances on QSO lines of sight may be correctand that observational determinations of primordial 4He may have systematicerrors. Plausible variations on n and Upsilon in our models do not change theresults much. If we drop or change the crucial Gamma_o constraint, lower valuesof Omega_M and eta_{10} are permitted. The constraint Gamma_o = 0.15 +- 0.04,derived recently from the IRAS redshift survey, favors Omega_M \approx 0.3 andeta_{10} \approx 5 but does not exclude eta_{10} \approx 2.Comment: Version accepted for ApJ. New section with figures showing effect of smaller Gamma; other minor changes. 18 pages including 14 ps figures; uses AAS LaTeX v4.