The Number Density of Intermediate‐ and High‐Luminosity Active Galactic Nuclei at z ∼ 2–3

Abstract

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 1044-1045 and 1043-1044 ergs s-1 and compare these 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 1043-1044.5 ergs s-1 and compare it 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 σ level.