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Session 29 - Dynamical Evolution of Galaxies.
Oral session, Monday, January 13
Harbour C,

[29.05] The Evolution of Elliptical Galaxies in Clusters

M. A. Pahre (Caltech)

The Fundamental Plane (FP) of elliptical is the set of bivariate correlations among the properties of elliptical galaxies. Observing the FP at a variety of wavelengths and redshifts provides a powerful tool for studying the underlying dynamical state, structures, stellar content, and formation processes of elliptical galaxies as a family. I will describe a series of observations of the FP and its projections which have the aim of identifying the origins of the FP: an imaging survey of 250 elliptical galaxies in 10 nearby rich clusters and 3 loose groups in the near--infrared K--band; (2) a two--color CCD imaging survey of rich clusters at 0.1 < z < 0.6 that allows the measurement of color evolution of the cluster elliptical galaxy population via the intercept of the restframe (U-V) color--magnitude relation; (3) a HST/WFPC--2 surface photometry study of ellipticals in distant clusters in order to measure their evolution via the intercept of the Kormendy radius--surface brightness relation; and (4) construction of the full FP in clusters at redshifts up to z \sim 0.55 using velocity dispersions and surface photometry from the Hale 5 m and Keck 10 m telescopes. The evolution of these relations suggests that the cluster elliptical galaxy population formed at high redshifts and is evolving passively. Furthermore, the slope of the FP in the optical and near--infrared cannot be explained by stellar populations alone; an additional wavelength--independent effect, such as systematic departures of elliptical galaxies from a homologous family, appears required.

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Program listing for Monday