F(2−12 keV)/(ν₂₅F₂₅) vs. HR4 diagnostic plot. Filled circles (black symbol in the electronic version only) are unabsorbed and absorbed Compton-thin AGN (N_H < 10²⁴ cm^-2) taken from two different X-ray samples in the literature (XMM-HBS sample – Della Ceca et al. 2008b; XMDS survey – Tajer et al. 2007; Polletta et al. 2007). Stars (blue objects in the electronic version only) are a sample of local star-burst galaxies (Ranalli et al. 2003) and squares (red objects in the electronic version only) and triangles (green objects in the electronic version only) are local “confirmed” and “candidate” Compton-thick AGN, respectively, taken by the compilation of Della Ceca et al. (2008a).