EDP Sciences
Free access
Volume 414, Number 1, January IV 2004
Page(s) 69 - 78
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20034113

A&A 414, 69-78 (2004)
DOI: 10.1051/0004-6361:20034113

The Small Magellanic Cloud in the far infrared

II. Global properties
K. Wilke1, U. Klaas1, D. Lemke1, K. Mattila2, M. Stickel1 and M. Haas1

1  Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
2  Helsinki University Observatory, Tähtitorninmäki, PO Box 14, 0014 University of Helsinki, Finland

(Received 24 July 2003 / Accepted 7 October 2003)

We present global IR properties of the Small Magellanic Cloud using an ISOPHOT 170 $\mu$m map and re-visited IRAS data. The integrated 170 $\mu$m flux is 14 950 $\pm$ 2300 Jy, and the integrated IR flux is $F_{1-1000} = 7.48 \times 10^{-10}$ W m -2. Discrete sources contribute 28%, 29%, and 36% to the integrated flux at 60 $\mu$m, 100 $\mu$m, and 170 $\mu$m, 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 $\mu$m and the IRAS 100  $\mu$m HiRes maps. The average dust temperature is $T_{\rm D} = 20.3$ K. The total dust mass is found to be $M_{\rm D} =
7.8\times 10^5\,M_{\odot}$ , yielding a gas-to-dust mass ratio $M_{\rm gas}$/ $M_{\rm dust} \approx 540$, a value 25 times lower than found by former studies. The global star formation rate is estimated to SFR $_{\rm total} \approx 0.05\,M_{\odot}$ yr -1. The comparison with other irregular galaxies reveals the SMC as quiet with no peculiar FIR properties.

Key words: galaxies: Magellanic Clouds -- ISM: general -- ISM: dust, extinction

Offprint request: U. Klaas, klaas@mpia.de

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