Star-forming galaxies as the origin of diffuse high-energy backgrounds: gamma-ray and neutrino connections, and implications for starburst history

By I. Tamborra, S. Ando, Kohta Murase. 2014

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Star-forming galaxies have been predicted to contribute considerably to the diffuse gamma-ray background as they are guaranteed reservoirs of cosmic rays. Assuming that the hadronic interactions responsible for high-energy gamma rays also produce high-energy neutrinos and that 𝒪(100) PeV cosmic rays can be produced and confined in starburst galaxies, we here discuss the possibility that star-forming galaxies are also the main sources of the high-energy neutrinos observed by the IceCube experiment. First, we compute the diffuse gamma-ray background from star-forming galaxies, adopting the latest Herschel PEP/HerMES luminosity function and relying on the correlation between the gamma-ray and infrared luminosities reported by Fermi observations. Then we derive the expected intensity of the diffuse high-energy neutrinos from star-forming galaxies including normal and starburst galaxies. Our results indicate that starbursts, including those with active galactic nuclei and galaxy mergers, could be the main sources of the high-energy neutrinos observed by the IceCube experiment. We find that assuming a cosmic-ray spectral index of 2.1–2.2 for all starburst-like galaxies, our predictions can be consistent with both the Fermi and IceCube data, but larger indices readily fail to explain the observed diffuse neutrino flux. Taking the starburst high-energy spectral index as free parameter, and extrapolating from GeV to PeV energies, we find that the spectra harder than E-2.15 are likely to be excluded by the IceCube data, which can be more constraining than the Fermi data for this population.

Subfields: Astronomy and Astrophysics, Atmospheric Science, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/f9b373bf7aa5f82dc498bb8e5ed3cf9e70ff3738

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Citations in the corpus

OBSERVATION AND CHARACTERIZATION OF A COSMIC MUON NEUTRINO FLUX FROM THE NORTHERN HEMISPHERE USING SIX YEARS OF ICECUBE DATA (2016, background): “…et al. 2013; Laha et al. 2013; Razzaque 2013; Roulet et al. 2013; Stecker 2013; Anchordoqui et al. 2014; Gonzalez-Garcia et al. 2014; Murase et al. 2014; Tamborra et al. 2014; Bechtol et al. 2015; Senno et al. 2016) that have been proposed to explain the observed astrophysical neutrino flux.”