The feeble radiative efficiency characteristic of Low-Luminosity Active Galactic Nuclei ( LLAGN ) is ascribed to a sub-Eddington accretion rate , typically at \log ( L _ { bol } / L _ { edd } ) \lesssim - 3 .
At the finest angular resolutions that are attainable nowadays using mid-infrared ( mid-IR ) interferometry , the prototypical LLAGN in NGC 1052 remains unresolved down to < 5 mas ( 0.5 pc ) .
This is in line with non-thermal emission from a compact jet , a scenario further supported by a number of evidences : the broken power-law shape of the continuum distribution in the radio-to-UV range ; the \sim 4 \% degree of polarisation measured in the nuclear mid-IR continuum , together with the mild optical extinction ( A _ { V } \sim 1 mag ) ; and the ‘ ‘ harder when brighter ’ ’ behaviour of the X-ray spectrum , indicative of self-Compton synchrotron radiation .
A remarkable feature is the steepness of the IR-to-UV core continuum , characterised by a power-law index of \sim 2.6 , as compared to the canonical value of 0.7 .
Alternatively , to explain the interferometric data by thermal emission would require an exceptionally compact dust distribution when compared to those observed in nearby AGN , with A _ { V } \gtrsim 2.8 mag to account for the IR polarisation .
This is in contrast with several observational evidences against a high extinction along the line of sight , including the detection of the nucleus in the UV range and the well defined shape of the power-law continuum .
The case of NGC 1052 shows that compact jets can dominate the nuclear emission in LLAGN across the whole electromagnetic spectrum , a scenario that might be common among this class of active nuclei .