The Cosmic Lens All-Sky Survey: statistical strong lensing, cosmological parameters, and global properties of galaxy populations

Extensive analyses of statistical strong gravitational lensing are performed based on the final Cosmic Lens All-Sky Survey (CLASS) well-defined statistical sample of flat-spectrum radio sources and current estimates of galaxy luminosity functions per morphological type. The analyses are carried out under the assumption that galactic lenses are well-approximated by singular isothermal ellipsoids and early-type galaxies evolved passively since redshift z similar to 1. Two goals of the analyses are: (i) to constrain cosmological parameters independently of other techniques (e.g. Type Ia supernovae magnitude-redshift relation, cosmic microwave background anisotropies, galaxy matter power spectra); and (ii) to constrain the characteristic line-of-sight velocity dispersion and the mean projected mass ellipticity for the early-type galaxy population. Depending on how the late-type galaxy population is treated (i.e. whether its characteristic velocity dispersion is constrained or not), we find for a flat universe with a classical cosmological constant that the matter fraction of the present critical density Omega(m) = 0.31(-0.14)(+0.27) (68 per cent) for the unconstrained case or 0.40(-0.16)(+0.28) (68 per cent) for the constrained case, with an additional systematic uncertainty of approximate to0.11 arising from the present uncertainty in the distribution of CLASS sources in redshift and flux density. For a flat universe with a constant equation of state for dark energy w = p(x)(pressure) /rho(x)(energy density) and the prior constraint w greater than or equal to -1, we find that -1 less than or equal to w< -0.55(-0.11)(+0.18) (68 per cent) for the unconstrained case or -1 less than or equal to w< -0.41(-0.16)(+0.28) (68 per cent) for the constrained case, where w = 1 corresponds to a classical cosmological constant. The determined value of the early-type characteristic velocity dispersion [sigma(*)((e))] depends on the faint-end slope of the early- type luminosity function [alpha((e))] and the intrinsic shape distribution of galaxies; for equal frequencies of oblates and prolates, we find that sigma(*)((e)) (0.3 less than or similar to z less than or similar to 1) = 198(-18)(+22) km s(-1) (68 per cent) for a 'steep' alpha((e)) = -1 or sigma(*)(e) (0.3 less than or similar to z less than or similar to 1) = 181(-15)(+18) km s(-1) (68 per cent) for a 'shallow' alpha((e)) = 0.54. Finally, from the relative frequencies of doubly imaged sources and quadruply imaged sources, we find that a mean projected mass ellipticity of early-type galaxies (epsilon) over bar (mass) = 0.42 with a 68 per cent lower limit of 0.28 assuming equal frequencies of oblates and prolates.