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Free keywords:
Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE
MPINP:
Theoretische Astrophysik - Abteilung Hofmann
Abstract:
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. We calculate the diffuse
neutrino and γ-ray fluxes produced by these CR protons interacting with
gas inside their sources. For a spectral slope of CRs close to α=2.1-2.2
as suggested by shock acceleration, we find that these UHECR sources contribute
the dominant fraction of both the isotropic $\gamma$-ray background and of the
extragalactic part of the astrophysical neutrino signal observed by IceCube.
