Ultra-High-Energy Cosmic Rays and other Messengers from Radio Galaxies

• Applicant: Dr. Björn Eichmann
• Subject Area: Astrophysics and Astronomy
• Term: from 2020 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 442523381

The origin of Ultra-High-Energy Cosmic Rays (UHECRs) is still one of the great enigmas of modern astroparticle physics. The identification of the sources of UHECRs using only these charged nuclei has been prevented up to now by their deflection in Galactic and extragalactic magnetic fields (EGMF). However, uncharged messengers like photons and neutrinos circumvent this problem and provide additional information.It has already been shown, that radio galaxies (RGs) - in particular their relativistic plasma outflows, the so-called jets - provide great potential of being one of the main sources. However, there is no complete explanation of all UHECR data so far. The proposed project intends to explain the contribution of RGs to the observed UHECRs including the accompanying secondary photons and neutrinos to constrain the necessary source properties. In this process, first a basic model of their jet dynamics will be developed that includes the interactions of the UHECRs within these sources. Those processes have already been investigated by both the host and the applicant, so that the first key objective is to combine these efforts yielding a comprehensive, multi-messenger model of RGs.Secondly, the open-access tool CRPropa will be used to propagate the UHECRs and theaccompanying secondaries from these sources to Earth. In this process, the impact of different, recent EGMF models on the UHECR propagation will be taken into account. Here, first constraints on the contribution of these sources with respect to their distance and source age will be derived, which marks the second key objective of the proposed project.Finally, a comprehensive fitting algorithm will be applied to determine the necessary properties of the jets of RGs, so that the observed flux, chemical composition and arrival directions of the UHECRs can be explained. Hereby, both the source properties known from radio observations and the constraints from high-energy neutrino and diffusive gamma-ray measurements are taken into account.In total the proposed project is a straight continuation of the previous work of the applicant, in which the latest model will be extended to a complete multi-messenger model of RGs that is subsequently probed on data. In this process, the comprehensive expertise of the host in multi-messenger astronomy will be of great benefit.

• DFG Programme: Research Fellowships
• International Connection: Norway
• Host: Professor Dr. Michael Kachelrieß