Diffuse Emission of Galactic High-Energy Gamma-Rays and Neutrinos from a Global Fit of Cosmic Rays

Abstract

In the standard picture of galactic cosmic rays, a diffuse flux of high-energy gamma-rays and neutrinos is produced from inelastic collisions of cosmic ray nuclei with the interstellar gas. The neutrino flux is a guaranteed signal for high-energy neutrino observatories such as IceCube, and first evidence was recently found. In gamma-rays, the LHAASO experiment also recently reported on the measurement of diffuse gamma-rays up to 1 PeV in energy. The measurements of these fluxes constitute an important test of the standard picture of galactic cosmic rays. Both the observation and non- observation allow important implications for the physics of cosmic ray acceleration and transport. We present CRINGE, a new model of galactic diffuse high-energy gamma-rays and neutrinos, based on a cosmic ray model that is obtained from a fit to data from AMS-02, DAMPE, IceTop as well as KASCADE. We discuss the uncertainties for the predicted emission from the cosmic ray model, but also from the choice of source distribution, gas maps and cross sections and consider the possibility of a contribution from unresolved sources. We find the overall uncertainty on the emission to vary between 10% and 30% at energies below 10 TeV and up to 50% above, with the uncertainty from the fit to CR data dominating in this energy range. The contribution from unresolved sources can potentially be of the same order of magnitude as the truly diffuse flux and can lead to significantly harder spectra. We compare the prediction of the CRINGE model with the recent data from LHAASO and IceCube and comment on the implications. Our fiducial model and cosmic ray spectra are publicly available on zenodo.