fluid and this new gas behaves as a dust-like matter at early times and as a X-type dark energy at late times. We will show in this paper that this model is a kind of interacting XCDM model, and constrain the parameters of this model by using observational data.

This paper is organized as follows. In Section 2, we introduce the extension version of the generalized Chaplygin gas, namely the NGCG model, to describe the unification of dark energy and dark matter, and demonstrate that the NGCG actually is a kind of interacting XCDM system. In Section 3, we analyze the NGCG model by means of the statefinder parameters. In Section 4, we constrain the parameters of the NGCG model using the SNe Ia, CMB, and LSS data. We give concluding remarks in the final section.

The NGCG scenario and the interacting XCDM parametrization
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In this section we introduce the NGCG model. In the framework of FRW cosmology, considering an exotic background fluid, the NGCG, described by the equation of state $$p_{\rm Ch} = - {\tilde{A}(a) \over \rho_{\rm Ch}^\alpha}~,
\label{eqstate}$$ where $\alpha$ is a real number and $\tilde{A}(a)$ is a function depends upon the scale factor of the Universe, 