Reconstructing the equation of state and density parameter for dark
  energy from combined analysis of recent SNe Ia, OHD and BAO data
  We adopt a model independent method to reconstruct the dark energy equation
of state by analyzing 5 sets of SNe Ia data along with Baryon Acoustic
Oscillation (BAO) and Observational Hubble Data (OHD). The SNe Ia data sets
include the most recent UNION2 data and other data compilations from the year
2007 to the present. We assume a closed form parametrization of the luminosity
distance in terms of redshift and perform a $\chi^2$ analysis of the
observational data. The matter density at the present epoch $\Omega_m^0$ is
also taken to be a parameter in the analysis and its best-fit values are
obtained for each of the data sets. We found a strong dependence of dark energy
equation of state on the matter density in the present and earlier epoch. From
the analysis, we also predict the lower limit of matter density parameter at an
earlier epoch within 1$\sigma$ confidence level for a flat FRW universe. The
dark energy equation of state appears to be a slow varying function of $z$. The
variation of dark energy density parameter and the matter density parameter are
also shown along with their 1$\sigma$ variations.
