Vol. 547
In section 3. Cosmology

Microwave and radio emission of dusty star-forming galaxies: Implication for the cosmic radio background

by N. Ysard and G. Lagache, A&A 547, A53

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The extragalactic background light, called the cosmic background, is dominated by the Big-Bang relic, or CMB (cosmic microwave background) in the radio domain. At other wavelengths it is dominated by the radiation emitted during the formation of stars and galaxies throughout the evolution of the Universe. In particular, the cosmic infrared background (CIB) is produced by dust heated by new stars in galaxies, and fitting the CIB can constrain the history of star formation in the Universe. An anomalous microwave component has been detected and is attributed to spinning dust. Recently, the ARCADE2 balloon experiment has discovered an excess of radiation in the cosmic radio background (CRB). The present article reports modeling the emission of galaxies, including synchrotron, free-free, and spinning dust emissions, in an effort to reproduce the CRB excess, taking the following observational data into account: number counts, redshift distribution of galaxies, cosmic background intensity, and anisotropies. As a result, it is impossible to reproduce all backgrounds, because if the CRB is fitted, then the previous agreement with the CIB is destroyed (cf figure). The authors conclude that if the radio emission measured by ARCADE2 has an astrophysical origin, then it has to originate in the Galaxy.