Unveiling a Population of X-ray Non-detected Agn

We define a sample of 27 radio-excess AGN in the Chandra Deep Field North by selecting galaxies that do not obey the radio/infrared correlation for radio-quiet AGN and star-forming galaxies. Approximately 60% of these radio-excess AGN are X-ray undetected in the 2 Ms Chandra catalog, even at exposures of ≥ 1 Ms; 25% lack even 2σ X-ray detections. The absorbing columns to the faint X-ray-detected objects are 1022 cm−2 < NH < 1024 cm−2, i.e., they are obscured but unlikely to be Compton thick. Using a local sample of radio-selected AGN, we show that a low ratio of X-ray to radio emission, as seen in the X-ray weaklyand nondetected samples, is correlated with the viewing angle of the central engine, and therefore with obscuration. Our technique can explore the proportion of obscured AGN in the distant Universe; the results reported here for radio-excess objects are consistent with but at the low end of the overall theoretical predictions for Comptonthick objects. Subject headings: galaxies: active — X-rays: galaxies — radio continuum: galaxies