Investigations of dust heating in M81, M83 and NGC 2403 with the Herschel Space Observatory

We use Spitzer Space Telescope and Herschel Space Observatory far-infrared data along with ground-based optical and near-infrared data to understand how dust heating in the nearby face-on spiral galaxies M81, M83 and NGC 2403 is affected by the starlight from all stars and by the radiation from star-forming regions. We find that 70/160 µm surface brightness ratios tend to be more strongly influenced by star-forming regions. However, the 250/350 µm and 350/500 µm surface brightness ratios are more strongly affected by the light from the total stellar populations, suggesting that the dust emission at >250 µm originates predominantly from a component that is colder than the dust seen at