CONSTRAINTS ON H, OMEGA(B) AND LAMBDA(0) FROM COSMIC MICROWAVE BACKGROUND OBSERVATIONS

In this paper we compare data to theory. We use a compilation of the m ost recent cosmic microwave background (CMB) measurements to constrain Hubble's constant h, the bar)ion fraction nbr and the cosmological co nstant lambda(0). We fit h-, Omega(b)- and lambda(o)-dependent power s pectra to the data. The models we consider are flat cold dark matter ( CDM) dominated universes with Bat (n(s) = 1)power spectra, thus the re sults obtained apply only to these models. CMB observations can exclud e more than half of the h - Omega(b) parameter space explored. The CMB data favor low values of Hubble's constant; h approximate to 0.35. Lo w values of Omega(b) are preferred (Omega(b) similar to 0.03) but the chi(2) minimum is shallow and we obtain Omega(b) < 0.28. A model with h approximate to 0.40, Omega(b) approximate to 0.15 and Omega(cdm) app roximate to 0.85 is permitted by constraints from the CMB data, BBN, c luster baryon fractions and the shape parameter Gamma derived from the mass density power spectra of galaxies and clusters. For flat-lambda( o) models, the CMB data, combined with BBN constraints exclude most of the h - lambda(o), plane. Models with Omega(o), approximate to 0.3, l ambda(o), approximate to 0.7 with h approximate to 0.75 are fully cons istent with the CMB data but are excluded by the strict new q(o) limit s from supernovae (Perlmutter et al. 1997). A combination of CMB data goodness-of-fit statistics, BBN and supernovae constraints in the h - lambda(o), plane, limits Hubble's constant to the interval 0.23 < h < 0.72.