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B. S. Ryden (Ohio State U.), D. A. Forbes, A. I. Terlevich (U. of Birmingham)
We test the hypothesis that the apparent shape of an elliptical galaxy is correlated with the age of its stellar population. The age estimates we use are based on luminosity-weighted absorption line indices, and are an indicator of the time since the last significant outburst of star formation in the galaxy. If, as our estimate of an elliptical galaxy's shape, we use the axis ratio of the isophote at the effective radius, we do not find a statistically significant correlation between age and shape. If, however, we use the axis ratio at only 1/16 the effective raidus, we find that ellipticals with ages greater than 8 Gyr are rounder in their inner regions than ellipticals with ages less than 8 Gyr; as measured by a KS test, the difference is significant at the P=0.0005 level for a sample of 34 galaxies. We discuss the implications of this shape difference in the context of the formation and evolution of elliptical galaxies.
The author(s) of this abstract have provided an email address for comments about the abstract: ryden@astronomy.ohio-state.edu