Active Galactic Nuclei and Quasars

The Kapteyn efforts dealing with Active Galaxies and QSOs (Quasi Stellar Objects) are concentrated around the following four key issues.

1. AGN unification and AGN radiation (an)isotropy
   Which are orientation invariants in active galaxies, and what is the magnitude of radiation anisotropy? What is the evidence for and against simple orientation unification, in radio-loud and radio-quiet AGN? How can one use unification to understand the cosmic evolution of the AGN phenomenon?
2. The nature of the FIR emission in radio-loud AGN
   Which mechanisms produce mid-IR and far-IR radiation in AGN, and how can these be used to constrain unification and starburst models? How do these mechanisms relate to the AGN radio-loudness, luminosity, host, environment, and redshift?
3. The AGN - starburst symbiosis
   Are AGN accretion and circumnuclear star-formation physically connected phenomena? Does this symbiosis evolve over cosmic time? If so, how?
4. The occurrence and the origin of nuclear activity in galaxies
   Which galaxies, nearby and far, display nuclear activity, and why? Which mechanism or combination of mechanisms drives/triggers black hole accretion in galaxies? Which parameters determine the nature of this accretion?