Generalized Chaplygin gas model: Constraints from Hubble parameter versus redshift data

We examine observational constraints on the generalized Chaplygin gas (GCG) model for dark energy from the 9 Hubble parameter data points, the 115 SNLS Sue la data and the size of baryonic acoustic oscillation peak at redshift, z = 0.35. At a 95.4% confidence level, a combination of three data sets gives 0.67 <= A(s) <= 0.83 and -0.21 <= alpha <= 0.42, which is within the allowed parameters ranges of the GCG as a candidate of the unified dark matter and dark energy. It is found that the standard Chaplygin gas model (alpha = 1) is ruled out by these data at the 99.7% confidence level. (c) 2006 Elsevier B.V. All rights reserved.