Type II quasars in the most luminous galaxies

An X-ray investigation of Type II active nuclei hosted in the hyperluminous infrared galaxies (HLIGs) is presented. Two classical HLIGs discovered in the IRAS survey, IRAS 09104+4109 and IRAS F15307+3252, are found to share many properties: 1) The active nuclei are absorbed by Compton-thick obscuring matter, and powered by well-grown (billions solar mass) black holes; 2) The large infrared luminosity appears to be due to hot/warm dust heated by the hidden active nuclei; 3) Both galaxies resides in a rich environment and are very luminous. In comparison, the HLIGs might be fundamemntally different from the local lower luminosity counterparts, ultra-luminous infrared galaxies (ULIGs) in their formation. The rich environment suggests that it could be a necessary condition to form the most luminous quasars, and their relation to high redshift radio galaxies is discussed briefly.