Hadronic-origin TeVγrays and ultrahigh energy cosmic rays from Centaurus A

Abstract

Centaurus A (Cen A) is the nearest radio-loud AGN and is detected from radio to very high-energy gamma rays. Its nuclear spectral energy distribution (SED) shows a double-peak feature, which is well explained by the leptonic $\mathrm{\text{synchrotron}}+\mathrm{\text{synchrotron}}$ self-Compton model. This model however cannot account for the observed high energy photons in the TeV range, which display a distinct component. Here, we show that $\ensuremath{\sim}\mathrm{TeV}$ photons can be well interpreted as the ${\ensuremath{\pi}}^{0}$ decay products from $p\ensuremath{\gamma}$ interactions of Fermi-accelerated high-energy protons in the jet with the seed photons around the second SED peak at $\ensuremath{\sim}170\text{ }\text{ }\mathrm{keV}$. Extrapolating the inferred proton spectrum to high energies, we find that this same model is consistent with the detection of two ultra-high-energy cosmic ray events detected by Pierre Auger Observatory from the direction of Cen A. We also estimate the GeV neutrino flux from the same process, and find that it is too faint to be detected by current high-energy neutrino detectors.