at Nikhef in H331
Speaker: Dr. David Berge (Nikhef/UvA)
Title: “A PeVatron at the Centre of the Milky Way”
Abstract:
As a bright and complex region seen at multiple wavelengths, the Galactic Centre has been a prime candidate for observations with the H.E.S.S. Imaging Atmospheric Telescope Array since data taking started in 2003. During over a decade of observation H.E.S.S. has revealed that in addition to a strong, point-like source coincident with the supermassive black hole Sgr A* the Galactic Centre region also contains a number of other sources.
Most notably diffuse TeV gamma-ray emission has been detected along the so called Galactic ridge. Extending over 200 parsec and correlating with molecular gas in the region, we believe that this emission is due to cosmic rays accelerated close to our super-massive black hole Sagittarius A*. With new and more sensitive H.E.S.S. observations we have recently discovered that the gamma-ray emission proofs the existence of Petaelectronvolt (PeV) protons in this central region of the Milky Way.
This is particularly interesting in the context of the quest for the sources of the Galactic cosmic rays, since this is the first observational evidence for a cosmic PeVatron in our Galaxy. With H.E.S.S. we are finally starting to approach energies at the so called “knee” of the cosmic-ray energy spectrum — presumably the maximum energies Galactic particle accelerators can efficiently achieve.