SFB1491 - CIM

Project Description

Starburst galaxies are the most numerous potential extragalactic sources of high-energy cosmic rays (CRs) in the nearby Universe. However, details on their CR contribution are not well known, although most of them provide non-thermal emission over a broad range of energies. Multiwavelength observations indicate that some starburst galaxies show a dominant non-thermal contribution from their central regions, indicating the presence of an active black hole. These active galactic nuclei (AGN)-starburst composites are of special interest, as both phenomena on their own are potential sources of the high-energetic CRs frequently referred to as the extragalactic CR component. The simultaneous energy release by multiple supernova events as well as by accretion and jet activity of the central black hole makes AGN-starburst composites very promising candidates for the direct detection of CR sources. With first Fermi detections (Ackermann et al., 2012), they started to become visible in high-energy gamma rays. And at least since the indications of high-energy neutrino emission from NGC 1068 (Aartsen et al., 2020), AGN-starburst composites are also a promising source class for future neutrino detections and may become one of the first-ever astrophysical neutrino sources.

 

In this project we will merge the AGN and the starburst scenarios into a single, spatiallydependent, two-component model in order to obtain an understanding of such composite cores. Moreover, we will address their contribution to the high-energy neutrino, photon, and CR flux at Earth. The theoretical part of this project is tightly connected to the experimental part, providing the necessary information from nearby objects, such as NGC 1068, NGC 4945, and Circinus, on magnetic, photon, and matter fields in order to constrain the model.

 

These issues relate directly to the major research questions of CIM by deepening the understanding of the role of the astrophysical link between starburst galaxies and active galaxies. Using cosmic-ray electrons and the connected radiation signatures as information, we will investigate CRs from GeV up to PeV energies and beyond. In matching theory and observations, we will test the plasma parameters of cosmic-ray acceleration and develop new results on the role of prompt leptons in the production of secondaries in the very dense cores of Seyfertstarburst composites. These improvements of the comparison of theory with data will not only move forward the understanding of the origin of the non-thermal emission, but will also help to understand the relation between starbursts with and without active cores and between radio-loud and radio-quiet AGN.