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T. Treu (UCLA), R. Ellis, T. Liao (Caltech), P. van Dokkum (Yale), DEEP2 Collaboration
We present the first result of a spectroscopic follow-up of 250 early-type galaxies in the GOODS-N field. Ultra deep Keck spectra (6-12 hrs) are used to derive stellar velocity dispersion and, together with GOODS photometry, to measure the evolution of the Fundamental Plane out to z=1.2. The implied evolution of the mass to light ratio is found to depend strongly on galaxy mass. The most massive E/S0 are old and dead, while evidence for continuing star formation is found in less massive galaxies. The implication of this ``downsizing" phenomenon in terms of cosmological models of galaxy formation is briefly discussed.
Funding from Hubble Fellowship HF-01167.01 and STScI grant AR-09920.01 is gratefully acknowledged.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.