We present wide-field 1.1mm continuum imaging of the nearby spiral galaxy M 33, conducted with the AzTEC bolometer camera on ASTE.We show that the 1.1mm flux traces the distribution of dust with T ̃ 20K. Combined with far-infrared imaging at 160μm, we derived the dust temperature distribution out to a galactic radius of ̃7 kpc with a spatial resolution of ̃150 pc. Although the 1.1mm flux was observed predominantly near star-forming regions, we found a smooth radial temperature gradient declining from ̃20K to ̃13K consistent with recent results from the Herschel satellite. Further comparisons of individual regions show a strong correlation between the cold dust temperature and the KS band brightness, but not with the ionizing flux. The observed results imply that the dominant heating source of cold dust at few hundred parsec scales is due to non-OB stars, even when associated with star-forming regions.
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