The hot star population in H II regions, H II galaxies, and starburst galaxies is often described in terms of the number of "equivalent" O stars of a single representative subtype and luminosity class needed to produce the ionizing luminosity deduced from the nebular recombination lines in the optical spectra. In this paper we define conversion factors η_0_, η_1_ and ζ_5000_ with which the total number of O V stars and their flux contribution at 5000 A can be derived from the number of these "equivalent" stars. These quantities depend primarily on three parameters: the slope and upper mass limit of the stellar mass function and the metallicity of the region. Using the latest stellar atmosphere and evolution models, we calculate η_0_, η_1_ and ζ_5000_ for a large number of values of these parameters. The results are presented in tabular as well as graphical form. We apply our results to two H II regions for which the hot star population are known and find that the predicted numbers of O stars agree well the observed counts. In addition, we describe a method by which the values of η_0_ and η_1_ and the observed emission-line fluxes can be used to place constraints on the allowed values of the slope and upper mass limit of the stellar mass function in a region.
No takes yet. Share an insight, caveat, or question.
William D. Vacca (1994) studied this question.