The Number Density of Intermediate and High Luminosity Active Galactic   Nuclei at z~2-3
  We use the combination of the 2 Ms Chandra X-ray image, new J and H band images, and the Spitzer IRAC and MIPS images of the Chandra Deep Field-North to obtain high spectroscopic and photometric redshift completeness of high and intermediate X-ray luminosity sources in the redshift interval z=2-3. We measure the number densities of z=2-3 active galactic nuclei (AGNs) and broad-line AGNs in the rest-frame 2-8 keV luminosity intervals 10^44-10^45 and 10^43-10^44 ergs/s and compare with previous lower redshift results. We confirm a decline in the number densities of intermediate-luminosity sources at z>1. We also measure the number density of z=2-3 AGNs in the luminosity interval 10^43-10^44.5 ergs/s and compare with previous low and high-redshift results. Again, we find a decline in the number densities at z>1. In both cases, we can rule out the hypothesis that the number densities remain flat to z=2-3 at above the 5-sigma level. 
A.J. Barger and L.L. Cowie