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Star-forming galaxies are a copious source of non-thermal radiation which spans over 20 dex in energy, from ultra-high energy gamma-rays at PeV scale down to radio emission at ueV energies. Most of this emission derives from energy losses of cosmic rays that pervade the interstellar medium. In this work we show how a galaxy model that requires only few input parameters that are easily observed, even for high redshift objects, and some basic, run-of-the-mill, assumptions is sufficient to reproduce their non-thermal spectra. We then utilise this knowledge to derive the contribution star-forming galaxies make to the diffuse isotropic gamma-ray background, explain the origin of the far-infrared radio correlation and simultaneously obtain radio spectral indices that match observation. |
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