From our compilation of luminous O and B stars and supergiants of all spectral types, we have calculated the U, B, and V luminosity functions for stars within 3 kpc in our galaxy and the Magellanic Clouds. The luminosity functions are quite similar at all wavelengths, and the slight differences observed reflect variations in the sample size and degree of completeness. In the range -9 <= M_v_ <= -7, we find that the U, B, and V luminosity functions in both our galaxy and the Clouds have a slope of roughly + 0.7. The present-day initial mass function has also been calculated for these samples of stars. Within the uncertainties, our results are consistent with ψ(M) [the number of stars per kpc per year per log (M/M_sun_)] proportional to (M)^-2^ for the 25-85 M_sun_ range. The slopes for the Magellanic Clouds may be slightly flatter than in our galaxy, but there is probably incompleteness at the lower mass intervals. The impact of a luminous young cluster on the luminosity and mass functions was studied through the addition of stars from the 30 Doradus region to our LMC sample. Although this addition nearly doubled our population of early O stars, the U, B, and V luminosity functions remained essentially unchanged. However, the slope of the initial mass function flattened with the addition of the 30 Doradus sample. This flattening may be artificially produced by the lack of faint late O and early B stars in the 30 Dor sample which have not yet been studied.
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Blaha et al. (1989) studied this question.