The<i>Herschel</i>Space Observatory view of dust in M81

Abstract

We use <i>Herschel<i/> Space Observatory data to place observational constraints on the peak and Rayleigh-Jeans slope of dust emission observed at 70–500 <i>μ<i/>m in the nearby spiral galaxy M81. We find that the ratios of wave bands between 160 and 500 <i>μ<i/>m are primarily dependent on radius but that the ratio of 70 to 160 <i>μ<i/>m emission shows no clear dependence on surface brightness or radius. These results along with analyses of the spectral energy distributions imply that the 160–500 <i>μ<i/>m emission traces 15–30 K dust heated by evolved stars in the bulge and disc whereas the 70 <i>μ<i/>m emission includes dust heated by the active galactic nucleus and young stars in star forming regions.