A novel multimessenger study of Starburst galaxies: implications for neutrino astronomy

Abstract

Starburst galaxies (SBGs) and more in general starforming galaxies (SFGs) represent a class of galaxies with a high star formation rate (up to 100 Mo/year). Despite their low luminosity, they can be considered as guaranteed ``factories'' of high energy neutrinos, being ``reservoirs'' of accelerated cosmic rays and hosting a high density target gas in the central region. The estimation of their point-like and diffuse contributions to the neutrino astrophysical flux measured by IceCube can be crucial to describe the diffuse neutrino spectral features as well as the peculiar point-like excess like NGC1068. To this aim we use the latest gamma-ray catalog of this class of objects to perform a multimessenger study and describe their gamma-ray emission through a calorimetric scenario. For the diffuse analysis we perform a blending of the measured spectral indexes and obtain a multi-component description of extragalactic background light (EGB), high energy starting events (HESE) and high-energy cascade IceCube data. Remarkably, we find that, differently from recent prototype scenarios, the spectral index blending allows starburst galaxies to account for up to 40\% of the HESE events at 95.4\% CL and favors a maximal energy of the accelerated cosmic rays at tens of PeV. For the point-like analysis we apply the calorimetric approach to the known SBGs within 100 Mpc, considering, where possible, a source-by-source description of the star formation rate. These results are then compared with what can be expected from IceCube, IceCube/Gen2 and the incoming KM3NeT.