Improved Cosmological Constraints from Gravitational Lens Statistics
Abstract
We combine the Cosmic Lens AllSky Survey (CLASS) with new Sloan Digital Sky Survey (SDSS) data on the local velocity dispersion distribution function of E/S0 galaxies, φ(σ), to derive lens statistics constraints on Ω_{Λ} and Ω_{m}. Previous studies of this kind relied on a combination of the E/S0 galaxy luminosity function and the FaberJackson relation to characterize the lens galaxy population. However, ignoring dispersion in the FaberJackson relation leads to a biased estimate of φ(σ) 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 redshiftmagnitude 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 Ω_{Λ}=0.740.78 for a spatially flat universe (where the range reflects uncertainty in the number of E/S0 lenses in the CLASS sample) and a 95% confidence upper bound of Ω_{Λ}<0.86. If φ(σ) instead evolves in accord with the extended PressSchechter theory, then the maximum likelihood estimate for Ω_{Λ} becomes 0.720.78, with the 95% confidence upper bound Ω_{Λ}<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.
 Publication:

The Astrophysical Journal
 Pub Date:
 March 2005
 DOI:
 10.1086/427910
 arXiv:
 arXiv:astroph/0401138
 Bibcode:
 2005ApJ...622...81M
 Keywords:

 Cosmology: Cosmological Parameters;
 Cosmology: Observations;
 Cosmology: Theory;
 Cosmology: Gravitational Lensing;
 Astrophysics
 EPrint:
 35 pages, 15 figures, to be published in ApJ