Cosmological parameters from velocities, cosmic microwave background and supernovae

We compare and combine likelihood functions of the cosmological parameters Ω_m, h and σ₈, from peculiar velocities, cosmic microwave background (CMB) and type Ia supernovae. These three data sets directly probe the mass in the Universe, without the need to relate the galaxy distribution to the underlying mass via a 'biasing' relation. We include the recent results from the CMB experiments BOOMERANG and MAXIMA-1. Our analysis assumes a flat Λ cold dark matter (ACDM) cosmology with a scale-invariant adiabatic initial power spectrum and baryonic fraction as inferred from big-bang nucleosynthesis. We find that all three data sets agree well, overlapping significantly at the 2σ level. This therefore justifies a joint analysis, in which we find a joint best-fitting point and 95 per cent confidence limits of Ω_m = 0.28 (0.17,0.39), h = 0.74 (0.64,0.86) and σ₈ = 1.17 (0.98,1.37). In terms of the natural parameter combinations for these data σ₈Ω^0.6_m = 0.54 (0.40,0.73), Ω_mh = 0.21 (0.16,0.27). Also for the best-fitting point, Q_rms-ps = 19.7 μK and the age of the Universe is 13.2 Gyr.