The Small Magellanic Cloud in the far infrared

Abstract

We present global IR properties of the Small Magellanic Cloud using an ISOPHOT 170 µm map and re-visited IRAS data. The integrated 170 µm flux is 14 950 ± 2300 Jy, and the integrated IR flux is F1−1000 = 7.48 × 10 −10 Wm −2 . Discrete sources contribute 28%, 29%, and 36% to the integrated flux at 60 µm, 100 µm, and 170 µm, respectively. Most of the total emission arises from diffuse emission regions surrounding the HII regions. The SED can be modelled by the composition of a 45 K, a 20.5 K and a 10 K blackbody component with emissivity index n = 2. A color temperature map is constructed from the ISOPHOT 170 µm and the IRAS 100 µm HiRes maps. The average dust temperature is TD = 20.3 K. The total dust mass is found to be MD = 7.8 × 10 5 M� , yielding a gas-to-dust mass ratio Mgas/Mdust ≈ 540, a value 25 times lower than found by former studies. The global star formation rate is estimated to SFRtotal ≈ 0.05 Myr −1 . The comparison with other irregular