Speaker
Description
We present our new model of very-high-energy (VHE) cosmic rays incorporating discrete distributions of cosmic-ray sources, allowing for a more realistic description of our Galaxy. Using our model, we investigate two diffusion regimes, namely homogeneous and inhomogeneous diffusion around the cosmic-ray sources, and show how to constrain the birthrate of PeVatrons supernova remnants (SNRs). We notably show that for homogeneous diffusion the number of detectable SNRs above $\sim100\,\rm{TeV}$ is of the order of a few and is nearly independent of the actual number of PeVatron SNRs in the Galaxy. This is due to the very fast diffusion of cosmic rays around their sources. On the other hand, we find that for inhomogeneous diffusion, the number of detectable PeVatron SNRs scales with their actual number in the Galaxy, allowing us to put constraints on it. Finally, we show that at VHE the diffuse gamma-ray background is inherently clumpy, owing to the small cosmic-ray density and the short residence time of cosmic rays in the Galaxy, and can also help to constrain the number of PeVatron SNRs in the Galaxy.
[1] S. Kaci, G. Giacinti, JCAP 01, 049 (2025).
