Viscous generalized Chaplygin gas as a unified dark fluid: including perturbation of bulk viscosity

In this paper, we continue our previous work of studying viscous generalized Chaplygin gas as a unified dark fluid but the bulk viscosity perturbations. By using the currently available cosmic observational data from SNLS3, BAO, HST, and recently released Planck, we obtain a constraint on the bulk viscosity coefficient: zeta 0 = 0.0000138(-0.0000105-0.0000138-0.0000138)(+0.00000614+0.0000145+0.0000212) in 1, 2, 3 sigma regions, respectively, via the Markov Chain MonteCarlo method. The result shows that when considering perturbations of the bulk viscosity, the current cosmic observations favor a smaller bulk viscosity coefficient.