High-energy gamma-ray and neutrino production in star-forming galaxies across cosmic time: Difficulties in explaining the IceCube data. (14th April 2018)

• Record Type: Journal Article
• Authors: Sudoh, Takahiro; Totani, Tomonori; Kawanaka, Norita
• Is Part Of: Publications of the Astronomical Society of Japan. Volume 70:Number 3(2018:Jun.)
• Publication Date: 2018-04-14
• Subjects: gamma rays: diffuse background -- gamma rays: galaxies -- neutrinos; Astronomy -- Periodicals; 520.5
• DOI: 10.1093/pasj/psy039
• Languages: English
• ISSNs: 0004-6264

Abstract

Abstract: We present new theoretical modeling to predict the luminosity and spectrum of gamma-ray and neutrino emission of a star-forming galaxy, from the star formation rate (ψ), gas mass ( M gas ), stellar mass, and disk size, taking into account production, propagation, and interactions of cosmic rays. The model reproduces the observed gamma-ray luminosities of nearby galaxies detected by Fermi better than the simple power-law models as a function of ψ or ψ M gas . This model is then used to predict the cosmic background flux of gamma-rays and neutrinos from star-forming galaxies, by using a semi-analytical model of cosmological galaxy formation that reproduces many observed quantities of local and high-redshift galaxies. Calibration of the model using gamma-ray luminosities of nearby galaxies allows us to make a more reliable prediction than previous studies. In our baseline model, star-forming galaxies produce about 20% of the isotropic gamma-ray background unresolved by Fermi, and only 0.5% of IceCube neutrinos. Even with an extreme model assuming a hard injection cosmic-ray spectral index of 2.0 for all galaxies, at most 22% of IceCube neutrinos can be accounted for. These results indicate that it is difficult to explain most of the IceCube neutrinos by star-forming galaxies, without violating the gamma-ray constraints from nearby galaxies.