2010ApJ...716.1579L

We measure the average mass properties of a sample of 41 strong gravitational lenses at moderate redshift (z ∼ 0.4-0.9) and present the lens redshift for six of these galaxies for the first time. Using the techniques of strong and weak gravitational lensing on archival data obtained from the Hubble Space Telescope, we determine that the average mass overdensity profile of the lenses can be fit with a power-law profile (ΔΣ {vprop} R ^{–0.86±0.16}) that is within 1σ of an isothermal profile (ΔΣ {vprop} R^–1) with velocity dispersion σ_v= 260±20 km/s. Additionally, we use a two-component de Vaucouleurs + Navarro-Frenk-White (NFW) model to disentangle the total mass profile into separate luminous and dark matter components and determine the relative fraction of each component. We measure the average rest frame V-band stellar mass-to-light ratio (Υ_ V_= 4.0±0.6 h M_☉/L_☉) and virial mass-to-light ratio (τ_ V_= 300±90 h M_☉/L_☉) for our sample, resulting in a virial-to-stellar mass ratio of M_vir/M_*= 75±25. Relaxing the NFW assumption, we estimate that changing the inner slope of the dark matter profile by ∼20% yields a ∼30% change in stellar mass-to-light ratio. Finally, we compare our results to a previous study using low-redshift lenses to understand how galaxy mass profiles evolve over time. We investigate the evolution of M_vir/M_*(z) = α(1 + z)^β, and find best-fit parameters of α = 51 ± 36 and β = 0.9±1.8, constraining the growth of virial-to-stellar mass ratio over the last ∼7 Gyr. We note that, by using a sample of strong lenses, we are able to constrain the growth of M_vir/M_*(z) without making any assumptions about the initial mass function of the stellar population.