Understanding the Fanaroff-Riley radio galaxy classification
  The simple, yet profoundly far-reaching classification scheme based on
extended radio morphologies of radio galaxies, the Fanaroff-Riley
classification has been a cornerstone in our understanding of radio galaxies.
Over the decades since the recognition that there are two basic types of radio
galaxy morphologies there have been several findings in different wavebands
that have reported properties on different scales. Although it is realized that
there may be intrinsic as well external causes an overarching view of how we
may understand the two morphological types is missing. With the radio
power-absolute magnitude relation (the Owen-Ledlow diagram) as backdrop we
review and develop an understanding of the two radio galaxy types in the light
of what is known about them. We have for the first time included the dust
properties of the two FR classes together with the relative orientations of
dust, host major axis and the radio axis to present a qualitative framework
within which to understand the conditions under which they form. (Abridged).
