2016MNRAS.461.2192C

We use 118 strong gravitational lenses observed by the SLACS, BOSS emission-line lens survey (BELLS), LSD and SL2S surveys to constrain the total mass profile and the profile of luminosity density of stars (light tracers) in elliptical galaxies up to redshift z ∼ 1. Assuming power-law density profiles for the total mass density, ρ=ρ₀(r/r₀)^–α, and luminosity density, ν=ν₀(r/r₀)^–δ, we investigate the power-law index and its first derivative with respect to the redshift. Using Monte Carlo simulations of the posterior likelihood taking the Planck's best-fitting cosmology as a prior, we find γ=2.132±0.055 with a mild trend [?]γ/[?]z_l=-0.067±0.119 when α=δ=γ, suggesting that the total density profile of massive galaxies could have become slightly steeper over cosmic time. Furthermore, similar analyses performed on sub-samples defined by different lens redshifts and velocity dispersions indicate the need of treating low-, intermediate- and high-mass galaxies separately. Allowing δ to be a free parameter, we obtain α=2.070±0.031, [?]α/[?]z_l=-0.121±0.078 and δ=2.710±0.143. The model in which mass traces light is rejected at >95 per cent confidence, and our analysis robustly indicates the presence of dark matter in the form of a mass component that is differently spatially extended than the light. In this case, intermediate-mass elliptical galaxies (200 km/s <σ_ap <= 300 km/s) show the best consistency with the singular isothermal sphere as an effective model of galactic lenses.