Does the AGN Unified Model Evolve with Redshift? Using the X‐Ray Background to Predict the Mid‐Infrared Emission of AGNs

Deep X-ray surveys by Chandra and XMM-Newton have resolved about 80% of the2-10 keV cosmic extragalactic X-ray background (CXRB) into point sources, themajority of which are obscured AGN. The obscuration might be connected toprocesses within the host galaxy, possibly the star-formation rate. Here, weuse the results of CXRB synthesis calculations as input to detailed Cloudysimulations in order to predict the evolution of AGN properties at severalmid-IR wavelengths. Computations were performed for three different evolutionsof the AGN type 2/type 1 ratio between z=0 and 1: where the ratio increased as(1+z)^{0.9}, as (1+z)^{0.3} and one with no redshift evolution. Models werecalculated with the inner radius of the absorbing gas and dust at 1 pc or at 10pc. Comparing the results of the calculations to combined X-ray and Spitzerdata of AGN shows that the predicted spectral energy distributions are a gooddescription of average AGNs found in the deep surveys. The existing dataindicates that the mid-IR emission from an average AGN is best described bymodels where the attenuating material is ~10 pc from the central engine. Wepresent the expected Spitzer cumulative number count distributions and theevolution of the total AGN (type 1 + type 2) luminosity function (LF) betweenz=0 and 1 at rest-frame 8 microns and 30 microns for the three evolutionaryscenarios. The mid-IR AGN LF will be an excellent tool to measure the evolutionof the covering factor of the gas and dust from z~0 to 1.Comment: 27 pages, 17 figures (12 in color), accepted by the Ap