Constraints on Omega_Lambda and Omega_m from Distant Type 1a Supernovae and Cosmic Microwave Background Anisotropies

We perform a combined likelihood analysis of the latest cosmic microwave background anisotropy data and distant Type 1a Supernova data of Perlmutter etal (1998a). Our analysis is restricted to cosmological models where structure forms from adiabatic initial fluctuations characterised by a power-law spectrum with negligible tensor component. Marginalizing over other parameters, our best fit solution gives Omega_m = 0.25 (+0.18, -0.12) and Omega_Lambda = 0.63 (+0.17, -0.23) (95 % confidence errors) for the cosmic densities contributed by matter and a cosmological constant respectively. The results therefore strongly favour a nearly spatially flat Universe with a non-zero cosmological constant.