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- Summer break...
- 06.09., Bjoern Eichmann (RUB, NTNU): Can radio galaxies solve the UHECR puzzle?
Abstract: The origin of the ultra-high-energy cosmic rays (UHECRs) is one of the great enigmas of modern astroparticle physics. Radio galaxies (RGs) - which were divided by Fanaroff and Riley into two classes (FR-I and FR-II) - show great potential to be the birthplace of these nuclei with energies above 1 EeV. In this talk some recent findings on the contribution of two individual, promising radio galaxies, Centaurus A and Cygnus A, will be discussed as well as the CR contribution from the bulk of these galaxies. Using the radio luminosity as a robust estimator for the CR luminosity, it is shown that the FR-I source Centaurus A is able to provide the dominant UHECR contribution at the highest energies. But there is an other contributor between 5 EeV and 30 EeV needed. The exceptionally bright radio source Cygnus A is a prominent source candidate, but it is shown in this talk, that the impact by the extragalactic magnetic field on the CR propagation causes some serious issues: Either the arrival directions of the CRs provide a high degree of anisotropy or the delay exceeds the source age. Alternatively, the low-energetic UHECRs can originate in the bulk of FR-I or FR-II sources. For such a scenario, the necessary jet dynamics of FR sources are discussed, showing that FR-I RGs can in principle provide the observed amount of UHECR energy as well as a proper spectral behavior. In contrast, the bulk of FR-II RGs most likely contribute less than 25%.
slidslideses
- 28.10., Alexander Rothkopf (UiS): Open Quantum Systems: Thermometry at the Extremes
Germano Nardini (UiS), Alexander Stasik (UiO)
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