Testing the Dark Energy with Gravitational Lensing Statistics
Abstract
We study the redshift distribution of two samples of earlytype gravitational lenses, extracted from a larger collection of 122 systems, to constrain the cosmological constant in the ΛCDM model and the parameters of a set of alternative dark energy models (XCDM, DvaliGabadadzePorrati, and Ricci dark energy models), in a spatially flat universe. The likelihood is maximized for Ω_{Λ} = 0.70 ± 0.09 when considering the sample excluding the Sloan Lens ACS systems (known to be biased toward large imageseparation lenses) and noevolution, and Ω_{Λ} = 0.81 ± 0.05 when limiting to gravitational lenses with image separation Δθ > 2'' and noevolution. In both cases, results accounting for galaxy evolution are consistent within 1σ. The present test supports the accelerated expansion, by excluding the null hypothesis (i.e., Ω_{Λ} = 0) at more than 4σ, regardless of the chosen sample and assumptions on the galaxy evolution. A comparison between competitive world models is performed by means of the Bayesian information criterion. This shows that the simplest cosmological constant model—that has only one free parameter—is still preferred by the available data on the redshift distribution of gravitational lenses. We perform an analysis of the possible systematic effects, finding that the systematic errors due to sample incompleteness, galaxy evolution, and model uncertainties approximately equal the statistical errors, with presentday data. We find that the largest sources of systemic errors are the dynamical normalization and the highvelocity cutoff factor, followed by the faintend slope of the velocity dispersion function.
 Publication:

The Astrophysical Journal
 Pub Date:
 August 2012
 DOI:
 10.1088/0004637X/755/1/31
 arXiv:
 arXiv:1206.4948
 Bibcode:
 2012ApJ...755...31C
 Keywords:

 cosmological parameters;
 gravitational lensing: strong;
 methods: statistical;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 14 pages, 10 figures, accepted for publication in The Astrophysical Journal. Updated to match print version