The variation of the dust temperature within late-type spiral galaxies

We use high resolution (HiRes) 60 and 100 micron data to investigate the variation of the dust temperature in a sample of 4 late-type spiral galaxies. We have investigated the radial variation of the azimuthally averaged 60 and 100 micron surface brightness profiles to see how the dust temperature (or, more correctly, the relative strength of the two components) varies as a function of radius within the galaxies. We find strong evidence for a decrease in the dust temperature (or an increase in the relative contribution of the 100 micron flux compared to the 60 micron flux) as a function of radius. We discuss these results in the light of the continuing debate as to whether massive star formation or the general interstellar radiation field is the major heating source of the dust.