NFW case: the 1, 2, 3σ (purple region, red region and orange region, respectively) confidence ellipses for the global best-fit parameters. The blue solid line shows the c−M_vir relation from numerical simulations, the dashed blue lines show its 10 percent uncertainty. The green region shows the c−M_vir relation from the local density values obtained by the Salucci et al. (2010) method taking the 10 percent uncertainty into account.