Observation Constraints on the Simplified GCG Model

A simplified version of generalized Chaplygin gas (GCG) as a dark energy model is studied. By using the latest 162 ESSENCE type Ia supernovae (Sne Ia) data, 30 high redshift Sne Ia data, the baryonic acoustic oscillation peak from SDSS and the CMB data from WMAP3, a strong constraint on this simplified GCG model is obtained. At the 95.4% confidence level we obtain 0.21≤Ω_m≤0.31 and 0.994≤α≤1.0 with the best fit Ω_m=0.25 and α=1. This best fit scenario corresponds to an accelerating universe with q₀≌-0.65 and z≌0.81 (a redshift of cosmic phase transition from deceleration to acceleration).