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

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

3. 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.

4. 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

5. 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: /nature17147

6. 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: /nature17147

7. 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: /nature17147

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

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

10. 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

11. 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’

12. 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.