Modified Chaplygin gas as a unified dark matter and dark energy model and cosmic constraints

A modified Chaplygin gas model (MCG), ρ MCG / ρ MCG0 =[ B s +(1− B s ) a −3(1+ B )(1+ α ) ] 1/(1+ α ) , as a unified dark matter model and dark energy model, is constrained by using current available cosmic observational data points which include type Ia supernovae, baryon acoustic oscillation and the 7-year full WMAP data points. As a contrast to the consideration in the literature, we do not separate the MCG into two components, i.e. dark mater and dark energy component, but we take it as a whole energy component—a unified dark sector. By using a Markov Chain Monte Carlo method, a tight constraint is obtained: , and .