Probing the cosmic acceleration history and the properties of dark energy from the ESSENCE supernova data with a model independent method

With a model independent method the expansion history H(z), the deceleration parameter q(z) of the universe and the equation of state w(z) for the dark energy are reconstructed directly from the 192 Sne Ia (type Ia supernovae) data points which are contained in the new ESSENCE (Equation of State: Supernovae Trace Cosmic Expansion) Sne Ia data and the high redshift Sne Ia data. We find that the evolving properties of q(z) and w(z) reconstructed from the 192 Sne Ia data seem to be weaker than those obtained from the Gold set, but stronger than those from the SNLS (Supernova Legacy Survey) set. With a combination of the 192 Sne Ia and BAO (Baryonic Acoustic Oscillation) data, a tight constraint on Ω_m0 is obtained. At the 1σ confidence level Ω_m0 = 0.278_-0.023^+0.024, which is highly consistent with the values from the Gold + BAO and SNLS + BAO data.