Intrinsic absorption in AGN protocluster members. The red histogram shows the distribution of the intrinsic absorption of the eight protocluster members (including the Spiderweb) for which a robust measurement of N_H has been possible. The blue dashed histogram shows the upper limits on N_H obtained for six sources. The black solid line shows the distribution of N_H expected in the model of Gilli et al. (2007) at the flux limit of our observations. The two Compton-thick candidates with a reflection-dominated spectrum are not included.