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Published March 1, 1979 | Published
Journal Article Open

Observations and interpretations of radial gradients of absorption features in galaxies


Observations are presented of equivalent widths for strong spectral features with λ > 5000 Å in the nuclei of five galaxies (M31, M32, M81, NGC 4472, and NGC 3115) as well as the radial gradients of line strength within these galaxies. A theoretical model for predicting the strengths of features in the integrated light of galaxies is also presented. It is concluded, on the basis of this limited sample of galaxies, that the changes in spectral features between galactic nuclei and within galaxies arise from a single causal factor, which is the overall metallicity of the galaxy. The range in nuclear abundance spanned by the five galaxies is a factor of 4. There is no evidence for nonsolar ratios among the elements with lines that have been studied, namely, Ca, Na, Mg, and Fe; specifically, the approximate constancy of the Fe blends within and between galaxies has a natural explanation. Furthermore, the nuclear metallicity ordering is the same as the ordering of M_v.

Additional Information

© American Astronomical Society • Provided by the NASA Astrophysics Data System. Received 1978 May 1; accepted 1978 September 7. The author is grateful to R. Aikens for his work on the electronic stability of the CID array and to R. Lynds for the use of his software for picture processing.

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Published - 1979ApJ___228__405C.pdf


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