We investigate observational constraints on the generalized Chaplygin gas ( GCG ) model as the unification of dark matter and dark energy from the latest observational data : the Union SNe Ia data , the observational Hubble data , the SDSS baryon acoustic peak and the five-year WMAP shift parameter .
It is obtained that the best fit values of the GCG model parameters with their confidence level are A _ { s } = 0.73 ^ { +0.06 } _ { -0.06 } ( 1 \sigma ) ^ { +0.09 } _ { -0.09 } ( 2 \sigma ) , \alpha = -0.09 ^ { +0.15 } _ { -0.12 } ( 1 \sigma ) ^ { +0.26 } _ { -0.19 } ( 2 \sigma ) .
Furthermore in this model , we can see that the evolution of equation of state ( EOS ) for dark energy is similar to quiessence , and its current best-fit value is w _ { 0 de } = -0.96 with the 1 \sigma confidence level -0.91 \geq w _ { 0 de } \geq - 1.00 .