The Small Magellanic Cloud in the far infrared

Abstract

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.

CO and CS in the Magellanic Clouds: a $\mathsf{\chi^2}$-analysis of multitransitional data based on the MEP radiative transfer model

“…Schwering & Israel (1989) however detected a FIR source at about 1 off the peak opacity coordinates. Wilke et al (2003) re-examined the HiRes 60 -and 100 µm IRAS maps of the region and found a cold FIR source, with an estimated dust temperature of T d ≈ 30 K, just 30 off the CO peak.…”

Far Infrared mapping of NGC 891

“…However, the peak of the spectral energy distribution (SED) from cold dust, lying at the long far-infrared (FIR) wavelengths, is outside the wavelength coverage of IRAS, and thus has not been readily accessible until recently. With a wavelength coverage extending to 240 µm and a superior intrinsic sensitivity as compared to IRAS, the ISOPHOT instrument on board ISO (Kessler et al 1996) was the first to directly measure the peak of the FIR SED for a number of nearby galaxies (Tuffs et al 1996 for NGC 6946; Haas et al 1998 for M 31;Wilke et al 2003 for the SMC, Hippelein et al 2003 for M 33), for smaller statistical samples (Krügel et al 1998;Siebenmorgen et al 1999;Contursi et al 2001), for serendipitously detected spirals (Stickel et al 2000), for the ISOPHOT Virgo Cluster Deep Sample (Tuffs et al 2002a,b;Popescu et al 2002;) and for the sample of Bright Revised Shapley Ames galaxies (Bendo et al 2002(Bendo et al , 2003.…”

The Small Magellanic Cloud in the far infrared

“…In Wilke et al (2003) (Paper I hereafter), a map of the Small Magellanic Cloud (SMC) obtained with ISOPHOT in the new 170 µm wavelength band was presented. In order to treat the ISO and IRAS data in an identical and reproducible way we obtained IRAS high resolution maps at 12, 25, 60 and 100 µm by requesting HiRes processing at IPAC.…”