Observational Studies of the Structure of Active Galactic Nuclei and QSOs

Direct observational information on the structures of the central objects of active galaxies and quasi-stellar objects is hard to come by. Most of what we believe about these regions is inferred from data concerning the emission line spectra, the spectral energy distributions of the featureless continuum, and the luminosities and variability of the active nucleus. Data on the polarization of light from active galaxies, especially spectropolarimetric data which distinguishes between lines and continua, can offer additional insight into the nature of the central object, to some extent more direct information insofar as it can provide geometrical as well as physical information.