STELLAR POPULATIONS AND THE STAR FORMATION HISTORIES OF LOW SURFACE BRIGHTNESS GALAXIES. II. H II REGIONS
Journal Article
·
· Astronomical Journal (New York, N.Y. Online)
- Department of Physics, University of Oregon, Eugene, OR 97403 (United States)
- Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States)
- Department of Physics, Cambridge University, Cambridge (United Kingdom)
The luminosities, colors, and H{alpha} emission for 429 H II regions in 54 low surface brightness (LSB) galaxies are presented. While the number of H II regions per galaxy is lower in LSB galaxies compared to star-forming irregulars and spirals, there is no indication that the size or luminosity function of H II regions differs from other galaxy types. The lower number of H II regions per galaxy is consistent with their lower total star formation rates. The fraction of the total L{sub H{alpha}} contributed by H II regions varies from 10% to 90% in LSB galaxies (the rest of the H{alpha} emission being associated with a diffuse component) with no correlation with galaxy stellar or gas mass. Bright H II regions have bluer colors, similar to the trend in spirals; their number and luminosities are consistent with the hypothesis that they are produced by the same H II luminosity function as spirals. Comparison with stellar population models indicates that the brightest H II regions in LSB galaxies range in cluster mass from a few 10{sup 3} M{sub Sun} (e.g., {rho} Oph) to globular-cluster-sized systems (e.g., 30 Dor) and that their ages are consistent with clusters from 2 to 15 Myr old. The faintest H II regions are comparable to those in the LMC powered by a single O or B star. Thus, star formation in LSB galaxies covers the full range of stellar cluster mass.
- OSTI ID:
- 22122880
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Journal Name: Astronomical Journal (New York, N.Y. Online) Journal Issue: 2 Vol. 146; ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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