The Contribution of Quasars to the Far-Infrared Background

Recent observational results obtained with SCUBA, COBE and ISO have greatlyimproved our knowledge of the infrared and sub-mm background radiation. Theselimits become constraining given the realization that most AGNs are heavilyobscured and must reradiate strongly in the IR/sub-mm. Here we predict thecontribution of AGNs to the IR/sub-mm background, starting from measurements ofthe hard X-ray background. We show that an application of what we know of AGNSpectral Energy Distributions (SEDs) and the IR background requires that asignificant fraction of the 10-150 micron background comes from AGNs. Thisconclusion can only be avoided if obscured AGNs are intrinsically brighter inthe X-rays (with respect to the optical-UV) than unobscured AGNs, contrary to``unified schemes'' for AGNs, or have a dust to gas ratio much lower (< 0.1)than Galactic. We show that these results are rather robust and not stronglydependent on the details of the modeling.Comment: 13 pages, 1 figure, Astrophysical Journal, in pres