3C 66B as a TeV radio galaxy

Abstract

Abstract The Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) Telescope collaboration reported the detection of a new very high energy source, MAGIC J0223+430, located close to the position of the blazar 3C 66A, considered a candidate TeV blazar since a long time. A careful analysis showed that the events with energies above 150 GeV are centred on the position of the Fanaro–Riley type I radio galaxy 3C 66B (at 6 arcmin from 3C 66A), with a probability of 95.4 per cent (85.4 per cent including systematic uncertainties) that the source is not related to 3C 66A. We present a model for the possible emission of 3C 66B based on the structured jet model already used to interpret the TeV emission of the radio galaxy M87. The model requires parameters similar to those used for M87 but a larger luminosity for the layer, to account for the more luminous TeV emission. We also show that the spectrum obtained by MAGIC can be interpreted as the combined emission of 3C 66B, dominating above ∼200 GeV, and 3C 66A. The high-energy emission from the latter source, being strongly attenuated by the interaction with the extragalactic background light, can only contribute at low energies. If we were to see the jet emission of 3C 66B at small viewing angles, we would see a spectral energy distribution closely resembling the one of S5 0716+714, a typical blazar.