Fiore, F.F.FioreGrazian, A.A.GrazianSantini, P.P.SantiniPuccetti, SimonettaSimonettaPuccetti2020-09-172020-09-172008-01-01https://hdl.handle.net/20.500.13025/1069The Astrophysical Journal, Volume 672, Issue 1, pp. 94-101.We make use of deep HST, VLT, Spitzer, and Chandra data on the Chandra Deep Field-South to constrain the number of Compton-thick AGNs in this field. We show that sources with high 24 mum-to-optical flux ratios and red colors form a distinct source population, and that their infrared luminosity is dominated by AGN emission. Analysis of the X-ray properties of these extreme sources shows that most of them (80%+/-15%) are indeed likely to be highly obscured, Compton-thick AGNs. The number of infrared-selected, Compton-thick AGNs with 5.8 mum luminosity higher than 10<SUP>44.2</SUP> ergs s<SUP>-1</SUP> turns out to be similar to that of X-ray-selected, unobscured, and moderately obscured AGNs with 2-10 keV luminosity higher than 10<SUP>43</SUP> ergs s<SUP>-1</SUP> in the redshift bin 1.2-2.6. This ``factor of 2'' source population is exactly what is needed to solve the discrepancies between model predictions and X-ray AGN selection.Galaxies ActiveGalaxies High-RedshiftX-Rays Diffuse Background10.1086/523348http://adsabs.harvard.edu/abs/2008ApJ...672...94F2008ApJ...672...94F