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The evolution of merger-remnants and elliptical galaxy
scaling relations
Duncan Forbes (Birmingham)
Estimating the age of elliptical galaxies from their stars has proved
difficult due to the age-metallicity degeneracy of old stellar
populations. Recently however this degeneracy has been broken by the
combination of stellar spectroscopy and new models. These
luminosity-weighted central ages are now available for many galaxies.
We show that show that a galaxy's position relative to the fundamental
plane depends on its age. In particular, we show that the fundamental plane
residuals, B--V colors and Mg$_2$ line strengths are consistent with
an ageing central burst superposed on an old stellar population. This
reinforces the view that these age estimates are tracing the last major
episode of star formation induced by a gaseous merger event.
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