The Cosmic Lens AllSky Survey: statistical strong lensing, cosmological parameters, and global properties of galaxy populations
Abstract
Extensive analyses of statistical strong gravitational lensing are performed based on the final Cosmic Lens AllSky Survey (CLASS) welldefined statistical sample of flatspectrum radio sources and current estimates of galaxy luminosity functions per morphological type. The analyses are carried out under the assumption that galactic lenses are wellapproximated by singular isothermal ellipsoids and earlytype galaxies evolved passively since redshift z~ 1. Two goals of the analyses are: (i) to constrain cosmological parameters independently of other techniques (e.g. Type Ia supernovae magnituderedshift relation, cosmic microwave background anisotropies, galaxy matter power spectra); and (ii) to constrain the characteristic lineofsight velocity dispersion and the mean projected mass ellipticity for the earlytype galaxy population. Depending on how the latetype 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 Ω_{m}= 0.31^{+0.27}_{0.14} (68 per cent) for the unconstrained case or 0.40^{+0.28}_{0.16} (68 per cent) for the constrained case, with an additional systematic uncertainty of ~0.11 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)/ρ_{x}(energy density) and the prior constraint w>=1, we find that 1 <=w < 0.55^{+0.18}_{0.11} (68 per cent) for the unconstrained case or 1 <=w < 0.41^{+0.28}_{0.16} (68 per cent) for the constrained case, where w=1 corresponds to a classical cosmological constant. The determined value of the earlytype characteristic velocity dispersion [σ^{(e)}_{*}] depends on the faintend slope of the earlytype luminosity function [α^{(e)}] and the intrinsic shape distribution of galaxies; for equal frequencies of oblates and prolates, we find that σ^{(e)}_{*}(0.3 <~z<~ 1) = 198^{+22}_{18} km s^{1} (68 per cent) for a `steep'α^{(e)}=1 or σ^{(e)}_{*}(0.3 <~z<~ 1) = 181^{+18}_{15} km s^{1} (68 per cent) for a `shallow'α^{(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 earlytype galaxies with a 68 per cent lower limit of 0.28 assuming equal frequencies of oblates and prolates.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 December 2003
 DOI:
 10.1111/j.13652966.2003.07092.x
 arXiv:
 arXiv:astroph/0211244
 Bibcode:
 2003MNRAS.346..746C
 Keywords:

 gravitational lensing;
 methods: statistical;
 galaxies: haloes;
 galaxies: kinematics and dynamics;
 galaxies: structure;
 cosmological parameters;
 Astrophysics
 EPrint:
 31 pages, 12figures, 6 tables, to appear in MNRAS (referee comments incorporated, a section on future prospects added)