169_A-0458

Title: Galaxy mass-to-light ratios at z > 1 from the Fundamental Plane: measuring the star formation epoch and mass evolution of galaxies

Scientific program:

We propose to measure galaxy masses and mass-to-light ratios at the highest possible redshifts. Using the upgraded FORS2 spectrograph on the VLT we will measure stellar velocity dispersions of early-type galaxies out to a redshift of 1.4, the highest possible redshift. Combined with HST and ISAAC/VLT photometry, these data can determine the evolution of the mass-to-light ratio of early-type galaxies through the ``Fundamental Plane''. The evolution of the mass-to-light ratio provides a very strong constraint on the epoch of star formation of these galaxies, and hence their formation history. Combining the mass-to-light ratios with the known luminosity functions of high redshift galaxies, the relevance of merging between z=0 and z=1.4 can be tested.