A complete disclosure of the hidden type-1 AGN in NGC 1068 thanks to 52
  years of broadband polarimetric observation
  We create the first broadband polarization spectrum of an active galactic
nucleus (AGN) by compiling the 0.1 - 100 microns, 4.9 GHz and 15 GHz continuum
polarization of NGC 1068 from more than 50 years of observations. Despite the
diversity of instruments and apertures, the observed spectrum of linear
continuum polarization has distinctive wavelength-dependent signatures that can
be related to the AGN and host galaxy physics. The impact of the Big Blue bump
and infrared bump, together with electron, Mie scattering, dichroism and
synchrotron emission are naturally highlighted in polarization, allowing us to
reveal the type-1 AGN core inside this type-2 object with unprecedented
precision. In order to isolate the AGN component, we reconstruct the spectral
energy distribution of NGC 1068 and estimate the fraction of diluting light in
the observed continuum flux. This allows us to clearly and independently show
that, in the case of NGC 1068, Thomson scattering is the dominant mechanism for
the polarization in the optical band. We also investigate the effect of
aperture on the observed polarization and confirm previous findings on the
extension of the narrow line region of NGC 1068 and on the B-band and K-band
polarization from the host. Finally, we do not detect statistically significant
aperture-corrected polarimetric variations over the last 52 years, suggesting
that the parsec-scale morphological and magnetic geometries probably remained
stable for more than half a century.
