Chemical Evolution of Galaxies
Gregory A. Shields
Department of Astronomy, University of Texas, Austin, Texas 78712
Abstract. Chemical abundances provide important clues to the evolution
of galaxies. Ionized nebulae are one of the main sources of chemical
abundance measurements, especially in external galaxies. Studies
of H II regions have shown that the overall metallicity of
galaxies increases with galactic luminosity, and that spiral
galaxies characteristically have radial gradients in chemical
composition. There are indications of environmental influences
on chemical abundances. Planetary nebulae provide another measure
of abundances in the Milky Way and other galaxies. Space
facilities have allowed measurements for elements that
are inaccessible at optical wavelengths. Large telescopes
make possible the study of individual stars in external galaxies
and the study of interstellar abundances in galaxies at
intermediate and high redshifts. These advances promise exciting
times as astrophysicists strive to paint a complete picture of
galactic evolution from the Big Bang to the present.
For a postscript version of the article, click
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INTRODUCTION
FOUNDATIONS
RADIAL GRADIENTS
ABUNDANCE FLUCTUATIONS
LUMINOSITY DEPENDENCE
EFFECT OF ENVIRONMENT
ABUNDANCES IN THE EARLY UNIVERSE
DISCUSSION
REFERENCES
