2009MNRAS.400..875L

For lensing galaxies, we introduce a formal velocity dispersion σ_lens, based on enclosed mass and the virial theorem. This is calculated from an ensemble of pixelated lens models, and found to be fairly model-independent. A sample of 18 well-known early-type lensing galaxies and two clusters is found to be consistent with σ_lens= σ_obs. Both the early-type lensing galaxies and the clusters can thus be determined as being virialized. In a second step, we calculate the I-band luminosity and the total mass content for the sample of lensing galaxies, which enables us to analyse the mass-to-light relation L ∝ M^α. We determine α = 0.70±0.08, excluding constant M/L and consistent with previous studies of the Fundamental Plane. Additionally, we verify that this relation does not extrapolate to clusters, which have a much higher M/L. The sample used for this analysis comprises nine lensing galaxies from the Sloan Lens ACS (Advanced Camera for Surveys) Survey and another nine from the CfA-Arizona Space Telescope LEns Survey as well as the lensing clusters ACO 1689 and ACO 2667.