Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1978
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1978apj...222..821s&link_type=abstract
Astrophysical Journal, Part 1, vol. 222, June 15, 1978, p. 821-832.
Astronomy and Astrophysics
Astrophysics
216
Abundance, Astronomical Models, Metal Ions, Nebulae, Photoionization, Spiral Galaxies, Astronomical Spectroscopy, Galactic Evolution, Galactic Radiation, H Ii Regions, Hydrogen Ions
Scientific paper
The interpretation of the spectra of H II regions in the disks of spiral galaxies is reconsidered along with the systematic variation of these spectra with distance from the center of a galaxy. Data of improved accuracy are presented for three previously studied H II regions in M101 and analyzed on the basis of models that take into account the effect of metal absorption edges in the ionizing stellar radiation. It is shown that an excellent fit to the observed spectra can be obtained if the three H II regions differ in the temperature of the ionizing stars and if the models employed are self-consistent in the sense that the ionizing stars have the same metal abundance as the gas. Reliable abundance estimates of the inner H II regions are obtained and used to investigate the form of the abundance-radius relation. The results indicate that the observed form is in conflict with the predictions of simple models of galactic evolution.
Searle Leonard
Shields Gregory A.
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