Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 1976
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1976a%26a....53..213c&link_type=abstract
Astronomy and Astrophysics, vol. 53, no. 2, Dec. 1976, p. 213-225.
Astronomy and Astrophysics
Astrophysics
18
Intergalactic Media, Line Spectra, Radiant Flux Density, Spiral Galaxies, Abundance, Galactic Structure, H Ii Regions, Stellar Temperature
Scientific paper
Effects of exciting-star temperature, gas density, and elemental abundances on emission-line spectra of extragalactic H II regions are investigated. Observational data concerning line-intensity gradients in disks of spiral galaxies are reviewed, and two types of models are considered for the structure of the H II regions: homogeneous or quasi-homogeneous and inhomogeneous. Abundances of various ions are deduced for centrally located and outlying extragalactic H II regions. The results show that the classical model of an H II region with two slightly inhomogeneous Stroemgren zones gives a very good fit to the line intensities observed in external galaxies, that line-intensity gradients across disks can be explained by strong gradients in heavy-element abundances, and that the He II zone in the innermost H II regions should have a temperature of 3000 K.
Collin-Souffrin Suzy
Joly Monique
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