Abstract

Results from the ARCADE 2 experiment reveal for the first time an extragalactic radio background that is surprisingly bright, far in excess of the integrated contribution of discrete radio sources that have been characterised by interferometric surveys to their current flux limits. The origin of the radio background has thus provoked some debate. Given what is known from an analysis of radio source count surveys and constraints from the other cosmological backgrounds, we have developed a model to explain the radio background which has interesting astrophysical limitations. In the first part of the talk, I will present the measurements performed by the balloon-borne ARCADE 2 experiment. In the second part, I will discuss how existing constraints disfavour some explanations of the radio background that have been proposed, and present the case that the background is produced largely by the radio emission of ordinary star forming galaxies above redshift 1 characterised by an evolving radio to far-infrared correlation.