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 data points, which contain the new ESSENCE 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 that obtained from the Gold set, but stronger than that from the SNLS set. With a combination of the 192 Sne Ia and BAO data, a tight constraint on $Omega_{m0}$ is obtained. At the $1sigma$ confidence level $Omega_{m0}=0.278^{+0.024}_{-0.023}$, which is highly consistent with that from the Gold+BAO and SNLS+BAO.