2003ApJ...587..143R

We investigate the evolution of mass-selected early-type field galaxies using a sample of 28 gravitational lenses spanning the redshift range 0≲z≲1. Based on the redshift-dependent intercept of the fundamental plane in the rest-frame B band, we measure an evolution rate of dlog(M/L)_B/dz=-0.56±0.04 (all errors are 1 σ unless noted) if we directly compare to the local intercept measured from the Coma Cluster. Refitting the local intercept helps minimize potential systematic errors and yields an evolution rate of dlog(M/L)_B/dz=-0.54±0.09. An evolution analysis of properly corrected aperture mass-to-light ratios (defined by the lensed image separations) is closely related to the Faber-Jackson relation. In the rest-frame B band, we find an evolution rate of dlog(M/L)_B/dz=-0.41±0.21, a present-day characteristic magnitude of M_*0=-19.70+5logh±0.29 (assuming a characteristic velocity dispersion of σ_DM*=225km/s), and a Faber-Jackson slope of γ_FJ=3.29±0.58. The measured evolution rates favor old stellar populations (mean formation redshift <z_f≫1.8 at 2 σ confidence for a Salpeter initial mass function and a flat Ω_m=0.3 cosmology) among early-type field galaxies and argue against significant episodes of star formation at z<1.