Model Independent Reconstruction of the Expansion History of the Universe and the Properties of Dark Energy

Abstract

We have improved upon the method of smoothing supernovae data to reconstruct the expansion history of the universe, h(z), using two latest datasets, Gold and SNLS. The reconstruction process does not employ any parameterisation and is independent of any dark energy model. The reconstructed h(z) is used to derive the distance factor A up to redshift 0.35 and the results are compared with the given value of A from detection of baryon acoustic oscillation peak (BAO). We find very good agreement be- tween supernovae observations and the results from BAO for Ω0m ≈ 0.276±0.023. The estimated values of Ω0m are completely model-independent and are only based on observational data. The derived values of Ω0m are then used to reconstruct the equation of state of dark energy, w(z). Using our smoothing method we can demonstrate that while SNLS data are in very good agreement with ΛCDM, the Gold sample slightly prefers evolving dark energy. We also show that proper estimation of the equation of state of dark energy at the high redshifts would be impossible at the current status of observations