Using mid-infrared and radio selection criteria , we pre-select a sample of candidate high-redshift type-2 quasars in the Subaru XMM-Newton Deep Field ( SXDF ) .
To filter out starburst contaminants , we use a bayesian method to fit the spectral energy distributions ( SEDs ) between 24- \mu m and B-band , obtain photometric redshifts , and identify the best candidates for high- z type-2 quasars .
This leaves us with 12 z _ { phot } \geq 1.7 type-2 quasar candidates in an area \sim 0.8 deg ^ { 2 } , of which only two have secure X-ray detections .
The two detected sources have estimated column densities N _ { H } \sim 2 & 3 \times 10 ^ { 27 } m ^ { -2 } , i.e .
heavily obscured but Compton-thin quasars .
Given the large bolometric luminosities and redshifts of the undetected objects , the lack of X-ray detections suggests extreme absorbing columns N _ { H } \mathrel { \hbox { \hbox to 0.0 pt { \hbox { \lower 2.0 pt \hbox { $ \sim$ } } } \raise 2 % .0 pt \hbox { $ > $ } } } 10 ^ { 28 } m ^ { -2 } are typical .
We have found evidence for a population of “ Compton-thick ” high-redshift type-2 quasars , at least comparable to , and probably larger than the type-1 quasar population , although spectroscopic confirmation of their AGN nature is important .