CONSTRAINTS ON COSMOLOGICAL PARAMETERS FROM RECENT MEASUREMENTS OF COSMIC MICROWAVE BACKGROUND ANISOTROPY

A key prediction of cosmological theories for the origin and evolution of structure in the Universe is the existence of a 'Doppler peak' in the angular power spectrum of cosmic microwave background (CMB) fluctu ations. We present new results from a study of recent CMB observations which provide the first strong evidence for the existence of a 'Doppl er peak' localized in both angular scale and amplitude. This first est imate of the angular position of the peak is used to place a new direc t limit on the curvature of the Universe, corresponding to a density o f Omega = 0.7(-0.5)(+0.8), consistent with a flat universe. Very low-d ensity 'open' universe models are inconsistent with this limit unless there is a significant contribution from a cosmological constant, For a flat standard cold dark matter dominated universe we use our results in conjunction with big bang nucleosynthesis constraints to determine the value of the Hubble constant as H-0 = 30 - 70 km s(-1) Mpc(-1) fo r baryon fractions Omega(b) = 0.05 to 0.2. For H-0 = 50 km s(-1) Mpc(- 1) we find the primordial spectral index of the fluctuations to be = 1 .1 +/- 0.1, in close agreement with the inflationary prediction of n s imilar or equal to 1.0.