Resolution of the Upper IMF in the Magellanic Clouds

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Session 34 -- Massive Hot Stars with the Hubble Space Telescope Part I
Oral presentation, Tuesday, 31, 1994, 8:30-12:30

[34.06] Resolution of the Upper IMF in the Magellanic Clouds

N.R.Walborn, J.W.MacKenty, A.Saha, R.L.White (STScI), J.Wm.Parker (GSFC/NRC)

The upper IMF is best determined in extragalactic systems but is subject to systematic error due to limited spatial resolution and the tendency of massive stars to occur in compact groups. Luminosities may be overestimated and numbers underestimated. The Magellanic Clouds offer the most favorable case, but even there spatial resolution is critical; hence, HST can contribute significantly to addressing this problem. We have obtained UBV frames with WF/PC I of three fields in the LMC (other than the 30 Doradus central cluster) and one in the SMC which contain examples of the most massive stars (spectral type O3). These fields are in the 30 Dor periphery, the LMC giant shell H II region N11, and NGC 346--the largest H II region in the SMC. Some objects with peculiar or apparently composite spectra are newly resolved into multiple components, while others with normal spectra remain unresolved at the 0.1 arcsec level, either result being of interest. There are implications for the interpretation of ground-based and HST spectroscopy, and for evolutionary relationships among peculiar objects. Deconvolved images, color-magnitude diagrams, and IMF results will be presented.

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