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C. Reed (Alma College)
Galactic latitudes and photographic magnitudes for large samples (N ~ 2000 – 4000) of OB stars within 10 degrees of the galactic plane and 4 kpc of the Sun are used to estimate the scale height and surface density of these objects, assuming a barometric extinction model. For a dust- layer of scale height of 100 pc, B-band extinction 2 mag/kpc, and mean OB-star absolute blue magnitude –4.5, we find a scale height of ~ 45 pc and surface density 26 stars per hundred thousand square parsecs. The total galactic OB-star population is estimated to be approximately 60000, and the rate of formation of such stars to be on the order of one every 40 years. This work was supported by NSF grant AST 97-31179.