Speaker
Description
Sgr A has long been considered the most promising PeVatron candidate in the Galactic Centre (GC). Cosmic rays accelerated by Sgr A interact with gas in the Central Molecular Zone, producing the GC ridge diffuse gamma-ray emission. A bright point-like gamma-ray source, HESS J1745−290, is observed coincident with Sgr A. While both components are expected to originate from Sgr A, their spectral cut-offs differ significantly. A consistent model that reconciles this discrepancy is desired to confirm the interpretation of Sgr A as the dominant PeVatron in the GC. I revisit a proposed explanation in which the apparent low-energy cut-off of HESS J1745−290 arises from gamma-ray attenuation in a strong infrared radiation field near Sgr A, likely produced by surrounding dust. By constructing a physical model and comparing it with observational constraints, I show that this attenuation scenario is insufficient to account for the observed spectral discrepancy. Alternative explanations are needed, such as lepto-hadronic emission scenarios or a transition in the cosmic-ray diffusion regime.
