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abstract: |
    We study $M/L$ evolution of early-type galaxies using dynamical modeling of resolved internal kinematics. This makes fewer assumptions than Fundamental Plane (FP) studies and provides a powerful new approach for studying galaxy evolution. We focus on the sample of 25 galaxies in clusters at $z \approx 0.5$ modeled in Paper I. For comparison we compile and homogenize $M/L$ literature data for 60 nearby galaxies that were modeled in comparable detail. The nearby sample obeys $\log (M/L)_B = Z + S \log(\sigma_{\rm eff}/[200 {\>{\rm km}\,{\rm s}^{-1}}])$, with $Z = 0.896 \pm 0.010$, $S = 0.992 \pm 0.054$, and $\sigma_{\rm
    eff}$ the effective velocity dispersion. The $z
    \approx 0.5$ sample follows a similar relation but with lower zeropoint. The implied $M/L$ evolution is $\Delta \log(M/L) /
    \Delta z = -0.457 \pm 0.046 \> {\rm (random)} \pm 0.078 \> {\rm
    (systematic)}$, consistent with passive evolution following high-redshift formation. This agrees with the FP results for this sample by van Dokkum & van der Marel. This confirms that FP evolution tracks $M/L$ evolution, which is an important verification of the assumptions that underly FP studies. However, while we find more FP evolution for galaxies of low $\sigma_{\rm eff}$ (or low mass), 