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AT seminar 28.6.2018 Anne Lemiere


There is growing evidence that the Galactic Centre (GC) is playing a key role in particle acceleration at the scale of the
Galaxy. The most prominent evidence is the presence of the huge outflows extending 10 kpc above the Galactic disk 
pervaded by energetic particles that were revealed by their GeV emission, the so-called Fermi bubbles. 
With its 4 10^6 Msol, the supermassive black hole (SMBH), Sgr A* can release enough energy to power the bubbles in a few 
million years if it enters a quasar phase. The central hundreds of parsecs also contain several tens millions solar masses 
of molecular gas, as well as hundreds of young and massive stars and many supernova remnants.
This very rich region has been monitored by the High Energy Stereoscopic System (H.E.S.S.) I array of ground-based 
Cherenkov telescopes since 2004. Observations have shown that the emission is dominated by the contribution of the point 
source HESS J1745􀀀2901, located at less than 7” from Sgr A*, and HESS J1747􀀀281 associated with the composite supernova 
remnant G0.9+0.1. After subtracting these two point sources, a hard (power law index of 2.3) diffuse emission extending 
over 1° in longitude was discovered in 2006, and interpreted as the result of an overabundance of cosmic-rays interacting with 
the dense matter distribution of the Central Molecular Zone (CMZ). Here we report the results of a detailed spectral and 
morphological study of the inner 200 pc of the Galactic Centre region based on almost ten years of observations by H.E.S.S. and 
discuss the question of the origin of the CR excess in the GC.
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