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We present an analysis of stellar populations and evolutionary history ofgalaxies in three similarly rich galaxy clusters MS0451.6-0305 (z=0.54),RXJ0152.7-1357 (z=0.83), and RXJ1226.9+3332 (z=0.89); based on high S/Nground-based optical spectroscopy and HST imaging for 17-34 members in eachcluster. We find no indication of evolution of sizes or velocity dispersionswith redshift at a given dynamical galaxy mass. We establish the FundamentalPlane (FP) and scaling relations between absorption line indices and velocitydispersions. We confirm the steeper FP at z=0.86 compared to the low redshiftFP, indicating (under the assumption of passive evolution) the formationredshift, z_form, depends on the galaxy velocity dispersion (or mass). z_formvaries from z_form=1.24+-0.05 at velocity dispersion of 125 km/s to 1.95+-0.25at 225 km/s. The three clusters and the low redshift sample follow similarscaling relations between absorption line indices and velocity dispersions. Thestrength of the higher order Balmer lines Hdelta and Hgamma implies z_form>2.8.From the line strengths we find that [M/H] for MS0451.6-0305 is about 0.2 dexbelow that of the other clusters, and confirm our previous result that[alpha/Fe] for RXJ0152.7-1357 is about 0.3 dex higher than that of the otherclusters. These differences between the high-redshift clusters and the lowredshift sample are inconsistent with a passive evolution scenario forearly-type cluster galaxies over the redshift interval studied. (abridged)

Stellar populations and evolution of early-type cluster galaxies: Constraints from optical imaging and spectroscopy of z=0.5-0.9 galaxy clusters