H.E.S.S. Collaboration, A. Abramowski et al. Presented by: Jeroen Maat

Contents Galactic cosmic rays H.E.S.S. collaboration Observations Possible sources Conclusions Outlook Figure: SMBH Sgr A*

Galactic cosmic rays High-energy radiation, mainly protons and heavier nuclei Origin: mainly SNRs Knee at approximately 5 PeV Source: W. Hanlon, University of Utah. http://www.physics.utah.edu/~whanlon/spectrum.html

Source: S. Klepser, DESY, H.E.S.S. collaboration High Energy Stereoscopic System Secondary particles’ Cherenkov radiation Photon production by pp-interaction Source: S. Klepser, DESY, H.E.S.S. collaboration

Source: HESS Collaboration. Nature 1–4 (2016) doi:10.1038/nature17147 Observations VHE g-ray image of Central Molecular Zone Hadronic origin favoured over leptonic origin Source: HESS Collaboration. Nature 1–4 (2016) doi:10.1038/nature17147

Source: HESS Collaboration. Nature 1–4 (2016) doi:10.1038/nature17147 Observations Increased high-energy cosmic ray density implies presence of high- energy accelerator Source: HESS Collaboration. Nature 1–4 (2016) doi:10.1038/nature17147

Source: HESS Collaboration. Nature 1–4 (2016) doi:10.1038/nature17147 Observations for Agrees with accelerator that injects particles at quasi- continuous rate Source: HESS Collaboration. Nature 1–4 (2016) doi:10.1038/nature17147

Source: HESS Collaboration. Nature 1–4 (2016) doi:10.1038/nature17147 Observations Evidence for ‘PeVatron’! HESS J1745-290 as source? Source: HESS Collaboration. Nature 1–4 (2016) doi:10.1038/nature17147

Possible sources Conditions: Located in inner 10 pc of Galaxy Continuous acceleration for at least thousands of years Accelerate to PeV-energies

Possible sources SNRs: Cannot accelerate to PeV-energies for more than a few decades Stellar clusters: Central cluster located in inner 10 pc of Galaxy, but is too small SMBH Sgr A*: Satisfies all conditions

Conclusions g-rays of hadronic origin There must be at least one ‘PeVatron’ in CMZ SNRs and stellar clusters excluded as PeV accelerators SMBH Sgr A* may be the ‘PeVatron’

Outlook Study PeV-protons by looking at Emitted neutrino’s Synchrotron-g’s (x-rays) from secondary electrons/positrons This requires improved sensitivity to neutrino’s. Synchrotron-g’s are overshadowed by x-rays from other sources.