Unified model for cosmic rays above $10^{17}$ eV and the diffuse gamma-ray and neutrino backgrounds

Understand

We investigate how the extragalactic proton component derived within the "escape model" can be explained by astrophysical sources.

• We consider as possible cosmic ray (CR) sources normal/starburst galaxies and radio-loud active galactic nuclei (AGN).
• We find that the contribution to the total extragalactic proton flux from normal and starburst galaxies is only subdominant and does not fit the spectral shape deduced in the escape model.
• In the case of radio-loud AGN, we show that the complete extragalactic proton spectrum can be explained by a single source population, BL Lac/FR I, for any of the potential acceleration sites in these sources.