The BL Lac heart of Centaurus A

We have observed emission from the nucleus of the closest radio galaxy, Cen taurus A, from the radio to the gamma-ray band. We construct, for the first time, its overall spectral energy distribution (SED) which appears to be i ntriguingly similar to those of blazars, showing two broad peaks located in the far-infrared band and at similar to0.1 MeV respectively. The whole nuc lear emission of Centaurus A is successfully reproduced with a synchrotron self-Compton model. The estimated physical parameters of the emitting sourc e are similar to those of BL Lacs, except for a much smaller beaming factor , as qualitatively expected when a relativistic jet is orientated at a larg e angle to the line of sight. These results represent strong evidence that Centaurus A is indeed a misoriented BL Lac, and provide strong support in f avour of the unification scheme for low-luminosity radio-loud active galact ic nuclei. Modelling of the SED of Centaurus A also provides further and in dependent indications of the presence of velocity structures in sub-parsec- scale jets.