Efstathiou, Andreas

We present optical/infrared broad-band filter polarimetry and optical spectropolarimetry of the powerful FR II galaxy 3C 321. The latter observations reveal a scattered broad component to the Hα emission line, detectable in polarized flux. This implies that 3C 321 is actually a quasar the continuum and broad-line region of which are obscured from direct view, possibly by the geometrically thick torus invoked in the unified theory of active galaxies.

We present optical spectropolarimetry along with optical and infrared broad-band filter polarimetry of selected warm [f(25 μm)/f(60 μm) ≥ 0.3] IRAS galaxies and other known Seyfert 2 galaxies. Broad lines in polarized flux have been detected in a number of type 2 IRAS galaxies. From a determination of the intrinsic polarization of the scattered radiation it has been possible to model the optical and near-IR flux density and degrees of polarization, for a number of objects, with a cone-based scattering geometry. In all these cases an additional polarizing mechanism was required to match the near-IR data, and this was successfully modelled by a dichroic view of the near-IR emitting regions through the postulated torus which surrounds the type 1 core. For those objects which show broad lines in polarized flux, and for which the intrinsic polarization of the scattered radiation could be calculated, the inclinations to the line of sight tend to be low. The broad Hα luminosities calculated for the IRAS galaxies are more typical of QSOs than Seyfert 1 galaxies. Only a fraction of the IRAS galaxies observed exhibit broad lines in polarized flux indicating that either the scattering region is also obscured, or the broad lines are thermally broadened and rendered unobservable, or the unified theory is incorrect. Evidence supporting the former case is presented.

We present near-infrared polarized images of the active galaxy NGC 1068. At these wavelengths, the counter-cone is observed in scattered light. At H (1.64 μm) we detect an absorption band across the counter-cone, which we interpret as absorption owing to the postulated torus. From a geometrical analysis we calculate that the torus is at a position angle of 32° ± 3° on the plane of the sky, at an inclination to the line of sight (defined with respect to the polar axis) of 42° ± 4°, with a physical diameter greater than 200 pc. These figures are consistent with those derived from our models for the scattering of nuclear radiation and for the far-infrared emission from the torus.