Very high-energy γ-ray flux per unit solid angle in the Galactic centre region (black data points). The spectrum of the GC ridge region, |ℓ|  <   1°, |b|  <   0.3°, is shown. Allerror bars show the 1σ standard deviation and are corrected to account for some background double counting due to the stacking procedure. The spectrum is fitted over an energy range up to 45 TeV. It can be described by a power law with a photon index of 2.28 ± 0.03_stat ± 0.2_syst and a differential flux at 1 TeV of 1.2 ± 0.04_stat ± 0.2_syst × 10⁻⁸ TeV ⁻¹ cm⁻² s⁻¹ sr⁻¹. For comparison, the blue line is the γ-ray spectrum resulting from a power-law proton spectrum with a cut-off at 1 PeV.