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Reb, Lennart; Fernandez-Ontiveros, Juan A.; Almudena Prieto, M.; Dolag, Klaus (2018): A lower limit to the accretion disc radius in the low-luminosity AGN NGC 1052 derived from high-angular resolution data. In: Monthly Notices of the Royal Astronomical Society, Vol. 478, No. 1: L122-L126
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We investigate the central sub-arcsec region of the low-luminosity active galactic nucleus NGC 1052, using a high-angular resolution data set that covers 10 orders of magnitude in frequency. This allows us to infer the continuum emission within the innermost similar to 17 pc around the black hole to be of non-thermal, synchrotron origin and to set a limit to the maximum contribution of a standard accretion disc. Assuming the canonical 10 per cent mass-light conversion efficiency for the standard accretion disc, its inferred accretion power would be too low by one order of magnitude to account for the observed continuum luminosity. We thus introduce a truncated accretion disc and derive a truncation radius to mass-light conversion efficiency relation, which we use to reconcile the inferred accretion power with the continuum luminosity. As a result we find that a disc providing the necessary accretion power must be truncated at r(tr) greater than or similar to 26 r(g), consistent with the inner radius derived from the observations of the Fe K alpha line in the X-ray spectrum of this nucleus. This is the first time to derive a limit on the truncation radius of the accretion disc from high-angular resolution data only.