We present an analysis of stellar populations and evolutionary history of galaxies 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 ) .
Our analysis is based on high signal-to-noise ground-based optical spectroscopy and Hubble Space Telescope imaging for a total of 17-34 members in each cluster .
Using the dynamical masses together with the effective radii and the velocity dispersions we find no indication of evolution of sizes or velocity dispersions with redshift at a given galaxy mass .
We establish the Fundamental Plane ( FP ) and scaling relations between absorption line indices and velocity dispersions .
We confirm that the FP is steeper at z \approx 0.86 compared to the low redshift FP , indicating that under the assumption of passive evolution the formation redshift , z _ { form } , depends on the galaxy velocity dispersion ( or alternatively mass ) .
At a velocity dispersion of \sigma = 125 km s ^ { -1 } ( Mass = 10 ^ { 10.55 } { M } _ { \sun } ) we find z _ { form } = 1.24 \pm 0.05 , while at \sigma = 225 km s ^ { -1 } ( Mass = 10 ^ { 11.36 } { M } _ { \sun } ) the formation redshift is z _ { form } = 1.95 _ { -0.2 } ^ { +0.3 } , for a Salpeter initial mass function .
The three clusters follow similar scaling relations between absorption line indices and velocity dispersions as those found for low redshift galaxies .
The zero point offsets for the Balmer lines depend on cluster redshifts .
However , the offsets indicate a slower evolution , and therefore higher formation redshift , than the zero point differences found from the FP , if interpreting the data using a passive evolution model .
Specifically , the strength of the higher order Balmer lines H \delta and H \gamma implies z _ { form } > 2.8 .
The scaling relations for the metal indices in general show small and in some cases insignificant zero point offsets , favoring high formation redshifts for a passive evolution model .
Based on the absorption line indices and recent stellar population models from Thomas et al .
we find that MS0451.6-0305 has a mean metallicity [ M/H ] approximately 0.2 dex below that of the other clusters and our low redshift sample .
We confirm our previous result that RXJ0152.7-1357 has a mean abundance ratio [ \alpha / Fe ] approximately 0.3 dex higher than that of the other clusters .
The differences in [ M/H ] and [ \alpha / Fe ] between the high-redshift clusters and the low redshift sample are inconsistent with a passive evolution scenario for early-type cluster galaxies over the redshift interval studied .
Low-level star formation may be able to bring the metallicity of MS0451.6-0305 in agreement with the low redshift sample , while we speculate whether galaxy mergers can lead to sufficiently large changes in the abundance ratios for the RXJ0152.7-1357 galaxies to allow them to reach the low redshift sample values in the time available .