A Compact Jet at the Infrared Heart of the Prototypical Low-Luminosity
  AGN in NGC 1052
  The feeble radiative efficiency characteristic of Low-Luminosity Active
Galactic Nuclei (LLAGN) is ascribed to a sub-Eddington accretion rate,
typically at $\log(L_{\rm bol}/L_{\rm edd}) \lesssim -3$. 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
$< 5\, \rm{mas}$ ($0.5\, \rm{pc}$). 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 ($A_V \sim 1\, \rm{mag}$); 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 $A_V
\gtrsim 2.8\, \rm{mag}$ 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.
