High-energy gamma-ray and neutrino backgrounds from star-forming galaxies

Star-forming galaxies have been predicted to contribute considerably to the isotropic diffuse gamma-ray background. The hadronic interactions responsible for high-energy gamma rays also produce high-energy neutrinos. Assuming that at least 100 PeV cosmic rays can be produced and confined in starburst galaxies, the expected intensity of the diffuse gamma-ray and high-energy neutrinos from star-forming galaxies has been derived by adopting the latest Herschel data up to z∼4z∼4. We find that starburst galaxies could be the main contributor to the high-energy neutrinos observed by the IceCube experiment. Taking the starburst spectral index as free parameter, our predictions are consistent with Fermi and IceCube data simultaneously for a E−2.15E−2.15 spectrum for all starburst-like galaxies.