Cold galaxies
  We use 350 mu angular diameter estimates from Planck to test the idea that
some galaxies contain exceptionally cold (10-13 K) dust, since colder dust
implies a lower surface brightness radiation field illuminating the dust, and
hence a greater physical extent for a given luminosity. The galaxies identified
from their spectral energy distributions as containing cold dust do indeed show
the expected larger 350 mu diameters. For a few cold dust galaxies where
Herschel data are available we are able to use submillimetre maps or surface
brightness profiles to locate the cold dust, which as expected generally lies
outside the optical galaxy.
