Slicing the Torus: Obscuring Structures in Quasars
  Quasars and Active Galactic Nuclei (AGNs) are often obscured by dust and gas.
It is normally assumed that the obscuration occurs in an oblate "obscuring
torus", that begins at the radius at which the most refractive dust can remain
solid. The most famous form of this torus is a donut-shaped region of molecular
gas with a large scale-height. While this model is elegant and accounts for
many phenomena at once, it does not hold up to detailed tests. Instead the
obscuration in AGNs must occur on a wide range of scales and be due to a
minimum of three physically distinct absorbers. Slicing the "torus" into these
three regions will allow interesting physics of the AGN to be extracted.
