Star-forming galaxies as the origin of the IceCube PeV neutrinos

TL;DR

This paper investigates how star-forming galaxies could be the source of IceCube's PeV neutrinos by modeling cosmic ray interactions and neutrino production based on galaxy properties and observed cosmic ray fluxes.

Contribution

It provides a detailed calculation of neutrino production efficiency in star-forming galaxies considering realistic galaxy parameters and links the accumulated neutrino flux to observed cosmic ray data.

Findings

Star-forming galaxies can produce enough neutrinos to explain IceCube observations.

Neutrino flux depends on cosmic ray confinement time in galaxies.

Model aligns neutrino spectrum with observed sub-PeV/PeV fluxes.

Abstract

Star-forming galaxies, due to their high star-formation rates and hence large number of supernova remnants therein, are huge reservoirs of cosmic rays (CRs). These CRs collide with gases in the galaxies and produce high-energy neutrinos through $pp$ collisions. In this paper, we calculate the neutrino production efficiency in star-forming galaxies by considering realistic galaxy properties, such as the gas density and galactic wind in star-forming galaxies. To calculate the accumulated neutrino flux, we use the infrared luminosity function of star-forming galaxies obtained by {\em Herschel} PEP/HerMES survey recently. The intensity of CRs producing PeV neutrinos in star-forming galaxies is normalized with the observed CR flux at EeV ({1\,EeV=$10^{18}\,$eV}), assuming that supernova remnants or hypernova remnants in star-forming galaxies can accelerate protons to EeV energies. Our calculations show that the accumulated neutrino emission produced by CRs in star-forming galaxies can account for the flux and spectrum of the sub-PeV/PeV neutrinos under reasonable assumptions on the CR confinement time in these galaxies.