Effectiveness of WISE colour-based selection techniques to uncover
  obscured AGN
  We present a highly reliable and efficient mid-infrared colour-based
selection technique for luminous active galactic nuclei (AGN) using the
Wide-field Infrared Survey Explorer (WISE) survey. Our technique is designed to
identify objects with red mid-infrared power-law spectral energy distributions.
We studied the dependency of our mid-infrared selection on the AGN intrinsic
luminosity and the effectiveness of our technique to uncover obscured AGN
missed in X-ray surveys. To do so we used two samples of luminous AGN
independently selected in hard X-ray and optical surveys. We used the largest
catalogue of 887 [OIII]5007-selected type 2 quasars (QSO2s) at z<0.83 in the
literature from the Sloan Digital Sky Survey (SDSS), and the 258 hard (>4.5
keV) X-ray-selected AGN from the Bright Ultrahard XMM-Newton Survey (BUXS). The
effectiveness of our mid-infrared selection technique increases with the AGN
luminosity. At high luminosities and at least up to z~1 our technique is very
effective at identifying both Compton-thin and Compton-thick AGN.
