Galactic gamma-ray and neutrino emission from interacting cosmic-ray nuclei

Abstract

We present a study of the expectations for very-high-energy (VHE) to ultra-high-energy (UHE) gamma-ray and neutrino emission from interacting cosmic rays in our Galaxy as well as a comparison to the latest results for the Galactic UHE diffuse emission. We demonstrate the importance of properly accounting for both the mixed cosmic-ray composition and the gamma-ray absorption. We adopt the wounded-nucleon model of nucleus interactions and provide parameterisations of the resulting gamma-ray and neutrino production. Nucleon shielding due to clustering inside nuclei is shown to have a measurable effect on the production of gamma rays and is particularly evident close to breaks and cutoffs in mixed-composition particle spectra. The change in composition around the 'knee' in the cosmic ray spectrum has a noticeable impact on the diffuse neutrino and gamma-ray emission spectra. We show that current and near-future detectors can probe these differences in the key energy range from 10 TeV to 1 PeV, testing the paradigm of the universality of the cosmic ray spectrum and composition throughout the Galaxy.

Gamma-rays and neutrinos from giant molecular cloud populations in the galactic plane

“…For example, [38] has reported a value 1.8 at 10 GeV and that increases to 2.6 at 1 PeV. Also, discerning the effects of a change in the ISM or CR density on this factor can be challenging, as the two are intertwined and difficult to untangle [106]. For all these difficulties, fixed value is generally used in the past [38,42,103,104,107,108].…”

Probing the particle spectrum of nature with evaporating black holes

“…Other possible backgrounds are the extra-galactic [84] and galactic [85][86][87][88][89][90] gamma-ray backgrounds. However, we find these backgrounds to be smaller than the misidentified cosmic ray background, unless the EBH happens to line up with a gamma ray point source or the galactic centre.…”