Heavy obscuration in X-ray weak AGNs
  We present observations in the 0.1-100 keV spectral band of 8 Seyfert 2 galaxies, obtained by means of BeppoSAX. These sources were selected according to their [OIII] optical emission line flux, to avoid biases against obscuration on the pc scale. All sources were detected. All of them are weak X-ray emitters, and most of them are characterized by prominent iron lines at 6.4-7 keV (EW > 500 eV) and by a flat continuum, indicative of heavy obscuration along our line of sight (N_H > 10^25 cm^-2 in most cases). These results 1) provide further evidence in favor of the unified scenario, and 2) indicate that the average obscuration of type 2 AGNs is very likely much higher than deduced by former X-ray surveys. These findings have important implications for the synthesis of the X-ray background. 
R. Maiolino, M. Salvati, L. Bassani, M. Dadina, R. Della Ceca, G.   Matt, G. Risaliti, G. Zamorani