The centrality dependence of ν2/ε: the ideal hydro limit and η/s

The large elliptic flow observed at RHIC is considered to be evidence for almost perfect liquid behavior of the strongly coupled quark-gluon plasma produced in the collisions. In these proceedings we present a two parameter fit for the centrality dependence of the elliptic flow ν2 scaled by the spatial eccentricity ε. We show by comparing to viscous hydrodynamical calculations that these two parameters are in good approximation proportional to the shear viscosity over entropy ratio η/s and the ideal hydro limit of the ratio ν2/ε.