Abstract. Infrared to millimetre spectral energy distributions (SEDs) have been obtained for 41 bright ultraluminous infrared galaxies (ULIRGs). The observations were carried out with ISOPHOT between 10 and 200 µm and supplemented for 16 sources with JCMT/SCUBA at 450 and 850 µm and with SEST at 1.3 mm. In addition, seven sources were observed at 1.2 and 2.2 µm with the 2.2 m telescope on Calar Alto. These new SEDs represent the most complete set of infrared photometric templates obtained so far on ULIRGs in the local universe. The SEDs peak at 60-100 µm and show often a quite shallow Rayleigh-Jeans tail. Fits with one single modified blackbody yield a high FIR opacity and small dust emissivity exponent β < 2. However, this concept leads to conflicts with several other observational constraints, like the low PAH extinction or the extended filamentary optical morphology. A more consistent picture is obtained using several dust components with β = 2, low to moderate FIR opacity and cool (50 K > T > 30 K) to cold (30 K > T > 10 K) temperatures. This provides evidence for two dust stages, the cool starburst dominated one and the cold cirrus-like one. The third stage with several hundred Kelvin warm dust is identified in the AGN dominated ULIRGs, showing up as a NIR-MIR powerlaw flux increase. While AGNs and SBs appear indistinguishable at FIR and submm wavelengths, they differ in the NIR-MIR. This suggests that the cool FIR emitting dust is not related to the AGN, and that the AGN only powers the warm and hot dust. In comparison with optical and MIR spectroscopy, a criterion based on the SED shapes and the NIR colours is established to reveal AGNs among ULIRGs. Also the possibility of recognising evolutionary trends among the ULIRGs via the relative amounts of cold, cool and warm dust components is investigated.

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 F 1−1000 = 7.48 × 10 −10 W m −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 T D = 20.3 K. The total dust mass is found to be M D = 7.8 × 10 5 M , yielding a gas-to-dust mass ratio M gas /M dust ≈ 540, a value 25 times lower than found by former studies. The global star formation rate is estimated to SFR total ≈ 0.05 M yr −1 . The comparison with other irregular galaxies reveals the SMC as quiet with no peculiar FIR properties.

Abstract. The ISOPHOT experiment onboard the ISO satellite generated a complete view of the Small Magellanic Cloud (SMC) at 170 µm with 1.5 arcmin resolution. The map is analysed using an automated photometry program enabling accurate photometric characterization of the far infrared (FIR) emitting regions. An integrated FIR luminosity of 8.5×10 7 L is obtained, leading to a star formation rate of SFR FIR = 0.015 M /yr. With an average dust temperature of < T D, 170/100 = 20.5 K >, the total dust mass follows to M D = 3.7 × 10 5 M . In this paper, the sources detected at 170 µm are compared with those obtainable from the IRAS satellite data. For this purpose, the 12 µm, 25 µm, 60 µm, and 100 µm IRAS high resolution (HiRes) maps of the SMC are re-examined using the same method. In contrast to former studies, this provides an all-band ISO/IRAS source catalog which is no longer based on eyeball classification, but relies on an algorithm which is capable of automated, repeatable photometry, even for irregular sources. In the mid infrared IRAS bands numerous bright FIR emitting regions in the SMC are detected and classified: 73 sources are found at 12 µm, 135 at 25 µm (most of them with F ν < 1.0 Jy). All three FIR bands at 170 µm, 100 µm, and 60 µm reproduce the overall morphological structure of the SMC similarly well, in contrast to the 12 µm and 25 µm maps which only contain a limited number of extended sources and do not trace the main body of the SMC. 243 sources are detected in the ISO 170 µm map, 155 of them with F ν ≥ 2.0 Jy. Comparable numbers are found for the two FIR IRAS maps at 60 µm (384) and 100 µm (338) with fluxes up to 450 Jy. 70 of the 243 170 µm sources are assigned a general SED type ("cold", "warm", i.e., <30 K, >30 K) for the first time. A comparison with earlier IRAS results suggests that many source flux densities in those studies have been under-or overestimated because of non-standardized fitting methods. Many sources with flux densities up to 40 Jy listed in former catalogs cannot be identified in our data.

No abstract

No abstract