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Recently the ARCADE 2 experiment measured the cosmic radio background (CRB)and found the brightness temperature of the CRB at 1.4 GHz to be ~480 mK.Integrating the flux density from the observed 1.4 GHz radio source countproduces a brightness temperature of ~100 mK---less than a quarter of theobserved CRB at 1.4 GHz. Radio quiet AGN are a large fraction of the 1.4 GHzuJy sources and typically host significant star formation. Thus, it is possiblethat AGN and host star formation could be responsible for some fraction of theexcess CRB at 1.4 GHz. Here, an X-ray background population synthesis model isused in conjunction with empirical radio to X-ray luminosity ratios tocalculate the AGN contribution to the CRB at 1.4 GHz including the emissionfrom host star formation. It is found that AGN and host star formationcontribute <~9% of the CRB at 1.4 GHz. When all known 1.4 GHz radio sourceclasses are considered, <~60% of the CRB at 1.4 GHz is accounted for;therefore, it is necessary that either known radio sources evolve significantlyat flux densities below current survey sensitivity limits or a new populationof low flux density radio sources exist.

Are Active Galactic Nuclei the Solution to the Excess Cosmic Radio Background at 1.4 GHz?