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Session 77 - Normal Galaxies.
Oral session, Thursday, June 13
Union Theater,
This study of star forming giant molecular clouds (GMCs) in the Magellanic Clouds is part of an effort to better understand the dependence of star formation on environment. The work involves the use of far-infrared (FIR) observations to measure the luminosity, dust temperature and star formation activity of individual GMCs and complexes of GMCs. The clouds studied are in two regions of the Large Magellanic Cloud (N11, and the region south of 30 Doradus), and one in the bar region of the Small Magellanic Cloud. The data used are from the IRAS High Resolution (HIRES) reprocessed data set, and the COBE Diffuse Infrared Background Explorer (DIRBE). The HIRES maps have a resolution of approximately 60'' at 60\mum and 75'' at 100\mum. The FIR data are compared with CO\,(J=1\!\rightarrow\!0) maps at a resolution of 40'' made with the SEST (15m).
The FIR luminosities of the observed clouds range from \sim3 \times 10^4 to 3 \times 10^6\,L_ødot. Virial masses derived from the CO data are compared with the FIR luminosities to give a star formation activity (FIR luminosity/virial mass) for each GMC. The star formation activities show a wide range of values virtually independent of cloud mass. The FIR luminosities are used to estimate the numbers and types of stars embedded in the GMCs. The DIRBE data are used along with the HIRES data to estimate the dust temperatures and optical depths in the observed regions. This allows a comparison between heating of the GMCs by the ISRF and by embedded sources. The properties of the Magellanic Cloud GMCs are compared with GMCs from the very different environment of the Milky Way.
