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Session 24 - Star Formation in the Galaxy & the LMC.
Display session, Tuesday, June 10
South Main Hall,

[24.09] A Reexamination of Galactic OB Associations

C. D. Garmany (U.Colorado)

The stellar population (IMF) and spatial size of massive star forming regions are important parameters for modeling the formation of massive stars, galactic chemical evolution, and potentially the distance scale of the universe. However, these quantities are not as well known as one might hope. Hodge (1986) has pointed out that the differing sizes of OB associations in nearby galaxies, as reported in the literature, could in some cases be explained by the observing material and selection criteria used. In our galaxy the situation is not much better, as anyone who has tried to find published members of given OB associations can attest. Only the closest have been studied using astrometric, spectroscopic and photometric criteria. This will improve with the publication of the HIPPARCOS data. But the stellar content of associations beyond about 1 kpc needs improvement. I have approached the problem by compiling a dataset of almost 10,000 galactic OB stars having UBV data and spectral types in the literature. I then compute individual stellar distances from these data to see if classically defined OB associations are recovered. While the 'finger of God" effect is a problem, there are some interesting realignments in association membership suggested by this technique.

Program listing for Tuesday