Reconstruction of Deceleration Parameters from Recent Cosmic Observations

In this paper, three kinds of simple parameterized deceleration parameters $q(z)=a+\frac{b z}{1+z}$, $q(z)=a+\frac{b z}{(1+z)^2}$ and $q(z)={1/2}+\frac{a z+b}{(1+z)^2}$ are reconstructed from the latest Sne Ia Gold dataset, observational Hubble data and their combination. It is found that the transition redshift from decelerated expansion to accelerated expansion $z_T$ and current decelerated parameter values $q_0$ are consistent with each other in $1\sigma$ region by only using Sne Ia Gold dataset and observational Hubble data in three parameterizations respectively. By combining the Sne Ia Gold dataset and observational Hubble data together, a tight constraint is obtained. With this combined constraints, $z_T$ is $0.505^{+0.080}_{-0.052}$, $0.368^{+0.059}_{-0.036}$, $0.767^{+0.121}_{-0.126}$ with $1\sigma$ error in three parameterizations respectively. And, it is easy to see that $z_T$ separates from each other in $1\sigma$ region clearly.