We combine the Cosmic Lens All-Sky Survey ( CLASS ) with new Sloan Digital Sky Survey ( SDSS ) data on the local velocity dispersion distribution function of E/S0 galaxies , \phi ( \sigma ) , to derive lens statistics constraints on \Omega _ { \Lambda } and \Omega _ { m } .
Previous studies of this kind relied on a combination of the E/S0 galaxy luminosity function and the Faber-Jackson relation to characterize the lens galaxy population .
However , ignoring dispersion in the Faber-Jackson relation leads to a biased estimate of \phi ( \sigma ) and therefore biased and overconfident constraints on the cosmological parameters .
The measured velocity dispersion function from a large sample of E/S0 galaxies provides a more reliable method for probing cosmology with strong lens statistics .
Our new constraints are in good agreement with recent results from the redshift-magnitude relation of Type Ia supernovae .
Adopting the traditional assumption that the E/S0 velocity function is constant in comoving units , we find a maximum likelihood estimate of \Omega _ { \Lambda } = 0.74 – 0.78 for a spatially flat unvierse ( where the range reflects uncertainty in the number of E/S0 lenses in the CLASS sample ) , and a 95 % confidence upper bound of \Omega _ { \Lambda } < 0.86 .
If \phi ( \sigma ) instead evolves in accord with extended Press-Schechter theory , then the maximum likelihood estimate for \Omega _ { \Lambda } becomes 0.72 – 0.78 , with the 95 % confidence upper bound \Omega _ { \Lambda } < 0.89 .
Even without assuming flatness , lensing provides independent confirmation of the evidence from Type Ia supernovae for a nonzero dark energy component in the universe .