  We present an analysis of deep mid- to far-infrared (MFIR) Spitzer
photometric observations of the southern 2Jy sample of powerful radio sources
(0.05 < z < 0.7), conducting a statistical investigation of the links between
radio jet, AGN, starburst activity and MFIR properties. This is part of an
ongoing extensive study of powerful radio galaxies that benefits from both
complete optical emission line information and a uniquely high detection rate
in the far-infrared (far-IR). We find tight correlations between the MFIR and
[OIII] emission luminosities, which are significantly better than those between
MFIR and extended radio luminosities, or between radio and [OIII] luminosities.
Since [OIII] is a known indicator of intrinsic AGN power, these correlations
confirm AGN illumination of the circum-nuclear dust as the primary heating
mechanism for the dust producing thermal MFIR emission at both 24 and 70
microns. We demonstrate that AGN heating is energetically feasible, and
identify the narrow line region clouds as the most likely location of the cool,
far-IR emitting dust. Starbursts make a major contribution to the heating of
the cool dust in only 15-28% of our targets.
  We also investigate the orientation dependence of the continuum properties,
finding that the broad- and narrow-line objects in our sample with strong
emission lines have similar distributions of MFIR luminosities and colours.
Therefore our results are entirely consistent with the orientation-based
unified schemes for powerful radio galaxies. However, the weak line radio
galaxies (WLRG) form a separate class of objects with intrinsically low
luminosity AGN in which both the optical emission lines and the MFIR continuum
are weak.
