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Session 51 - Galaxy Evolution and the Intergalactic Medium.
Display session, Wednesday, June 10
Atlas Ballroom,

[51.01] The Physical Parameters Underlying the Sequence of Early-Type Galaxies

M. A. Pahre (Caltech and CfA), S. G. Djorgovski (Caltech), R. R. de Carvalho (Caltech and ON/Brazil)

The physical parameters varying along the sequence of early-type galaxies are explored using the Fundamental Plane (FP) correlations in the local universe and in distant clusters.

The nearby galaxy samples in the UBVRIK bandpasses are drawn from a new survey (Pahre 1998) and the literature. A distant-independent parameterization of \Delta ( \log r_eff - 0.32 \langle \mu \rangle_eff ) against \log \sigma_0 shows that the slope A of the FP relation r_eff \propto \sigma_0^A \langle \Sigma \rangle_eff^B increases systematically with wavelength from U to K. A model is constructed to describe this variation of the FP slope, the slope of the Mg_2--\sigma_0 relation, and the effects of stellar populations gradients. This model shows that there are systematic variations of up to a factor of three in age and metallicity along the full range of the early-type galaxy sequence (in the sense that the most luminous galaxies are the oldest and the most metal rich), and that a wavelength-independent effect (such as dynamical homology breaking or systematic variations in dark matter content) is required. This model predicts that the slope of the FP evolves: the power-law index A should decrease with redshift.

A large sample of > 100 early-type galaxies in six clusters at 0.1

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