Infrared Surveys for AGN

From the earliest extragalactic infrared studies AGN have shown themselves to be strong infrared sources and IR surveys have revealed new populations of AGN. I briefly review current motivations for AGN surveys in the infrared and results from previous IR surveys. The Luminous Infrared Galaxies, which in some cases house dust-enshrouded AGN, submillimeter surveys, and recent studies of the cosmic x-ray and infrared backgrounds suggest that there is a population of highly-obscured AGN at high redshift. ISO Surveys have begun to resolve the infrared background and may have detected this obscured AGN population. New infrared surveys, particularly the SIRTF Wide-area Infrared Extragalac-tic Legacy Survey (SWIRE), will detect this population and provide a platform for understanding the evolution of AGN, Starbursts and passively evolving galaxies in the context of large-scale structure and environment. There are a number of motivations for infrared studies of AGN and for carrying out surveys for AGN at infrared wavelengths: 1. AGN unification models require a dusty, molecular obscuring screen (torus?) which is expected to emit in the infrared. 2. Cosmic X-Ray Background models require a population of highly obscured AGN which may be detectable in the infrared. 3. Infrared/Starburst emission is a frequent companion to AGN activity; IR emission originates from dust which is either associated with the active nucleus (e.g. the PG QSO sample; Sanders et al. 1989) or with circumnu-clear starburst emission as in the classical Seyfert galaxies NGC 1068 & NGC 7469. 4. Luminous Infrared Galaxies frequently harbor AGN cores and may be a stage in the development of AGN from the merger of gas-rich galaxies.