Planck Early Results: The Planck View of Nearby Galaxies
  The all-sky coverage of the Planck Early Release Compact Source Catalogue
(ERCSC) provides an unsurpassed survey of galaxies at submillimetre (submm)
wavelengths, representing a major improvement in the numbers of galaxies
detected, as well as the range of far-IR/submm wavelengths over which they have
been observed. We here present the first results on the properties of nearby
galaxies using these data. We match the ERCSC catalogue to IRAS-detected
galaxies in the Imperial IRAS Faint Source Redshift Catalogue (IIFSCz), so that
we can measure the spectral energy distributions (SEDs) of these objects from
60 to 850 microns. This produces a list of 1717 galaxies with reliable
associations between Planck and IRAS, from which we select a subset of 468 for
SED studies, namely those with strong detections in the three highest frequency
Planck bands and no evidence of cirrus contamination. The SEDs are fitted using
parametric dust models to determine the range of dust temperatures and
emissivities. We find evidence for colder dust than has previously been found
in external galaxies, with T<20K. Such cold temperatures are found using both
the standard single temperature dust model with variable emissivity beta, or a
two dust temperature model with beta fixed at 2. We also compare our results to
studies of distant submm galaxies (SMGs) which have been claimed to contain
cooler dust than their local counterparts. We find that including our sample of
468 galaxies significantly reduces the distinction between the two populations.
Fits to SEDs of selected objects using more sophisticated templates derived
from radiative transfer models confirm the presence of the colder dust found
through parameteric fitting. We thus conclude that cold (T<20K) dust is a
significant and largely unexplored component of many nearby galaxies.
