Constraints on the radial distance R of the ionized absorbing material from the central engine visualized in the log R − log ΔR plane, where ΔR resembles the diameter of the intrinsic absorber. The regions filled with light red can be excluded based on spectral results of Suzaku and the relations denoted along the border lines. The dashed line follows the relation ΔR = N_HR²ξ/L_ion with the appropriate average parameters derived from spectral fits to all Suzaku observations. The intersecting points with lines where ΔR<N_H/n_H marks the upper limit on R.