Evidence for a large fraction of Compton-thick quasars at high redshift

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-� m and B-band, obtain photometric redshifts, and identify the best candidates for high-z type-2 quasars. This leaves us with 12 zphot > 1.7 type-2 quasar candidates in an area � 0.8 deg 2 , of which only two have secure X-ray detections. Given the large bolometric luminosities and redshifts of the objects, the lack of X-ray detections suggests extreme absorbing columns NH > 10 28 m 2 are typical. We conclude that we have found a population of “Compton-thick” highredshift type-2 quasars, at least comparable to, and probably larger than the type-1 quasar population.