Speaker
Description
Cosmic rays (CRs) can be accelerated in voilent and magnetised astrophysical environment. Those with the highest energyies, up to 10^20 eV are likely associated with star-formation in galaxies and active galactic nuclei activities. Cosmological filaments connect these acceleration sites of CRs, as well as with voids. Due to hadronic pion-producing and photo-pair interactions, and entrainment by magnet fields, some CRs can not be observed directly observed on Earth. To study this elusive population of CRs, we adopt an ecological approach which treats galaxies, clusters/superclusters and voids as key components in the filament ecosystem. Each component are permeated by magnetic fields with a variety of topologies, leading to different types of interfaces between these magnetic fields. We derive the phenomenology for modelling the transport of CRs in this ecosystem, adopting various magnetic field configurations and analyse the consequent fate of CRs. Our analysis shows that CRs are constrained and guided by the magnetic fields and their tranportation between different components are determined by the energies of the CRs and the properties of the interfaces in the filament ecosystem. Notably, Filaments act as ‘highways’, channelling CRs between other components (i.e. galaxies, galaxy clusters and superclusters), and as cosmic ‘fly paper’, capturing CR protons (with energies up to 10^18 eV) from voids. We also show that there is an accumulated population of CR protons of ∼ 10^12 − 10^16 eV, as they do not suffer significant energy losses through photo-pair or pion-production and cannot be cooled efficiently. They therefore form a CR fossil record of the power generation history of the Universe.
