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On the determination of the number of O stars in H II regions and starburst galaxiesThe 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 eta(sub 0), eta(sub 1), and zeta(sub 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 eta(sub 0), eta(sub 1), and zeta(sub 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 eta(sub 0) and eta(sub 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.
Document ID
19950035672
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Vacca, William D.
(University of California, Berkeley, CA United States)
Date Acquired
August 16, 2013
Publication Date
January 20, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 421
Issue: 1
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A67271
Funding Number(s)
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other

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