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N. Panagia (STScI), G. De Marchi (ESA)
We show how multi-band stellar photometry can effectively be used to determine simultaneously the properties of a stellar population and the characteristics of the intervening dust. Our method exploits the fact that all stars in an external galaxy are at one and the same distance, and makes use of the properties of red giant stars of the Red Clump to complement the information provided by young B-type stars. Thus, our method is suitable to study populations comprising also stars older than about 0.5 Gyr. Moreover, our method works even when (a) there is differential or patchy extinction, (b) the stellar population is the result of several bursts of star formation, or (c) there is considerable nebular emission. As an application, we discuss in detail the case of a region in the Large Magellanic Cloud, observed with the HST-WFPC2 in the U, B, V, I and H-alpha bands as part of the WFPC2 pure parallel programme. This field is located about 6 arcmin SW of the Tarantula Nebula (30 Dor) and displays large variations of the extinction, by as much as 3 magnitudes in AV. Our method allows us to determine the relative three-dimensional distribution of the different populations as well as their location with respect to the dust clouds. We derive the extinction law for this region and use it to place constraints on the properties of the absorbing dust.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.