The Sloan Lens ACS Survey. VI: Discovery and analysis of a double Einstein ring

Raphael Gavazzi; Tommaso Treu; Leon V. E. Koopmans; Adam S. Bolton; Leonidas A. Moustakas; Scott Burles; Philip J. Marshall

doi:10.1086/529541

paper

The Sloan Lens ACS Survey. VI: Discovery and analysis of a double Einstein ring

arXiv:0801.1555 · doi:10.1086/529541

Abstract

We report the discovery of two concentric Einstein rings around the gravitational lens SDSSJ0946+1006, as part of the Sloan Lens ACS Survey. The main lens is at redshift zl=0.222, while the inner ring (1) is at zs1=0.609 and Einstein radius $R e_{1} = 1.43 \pm 0.01"$ . The wider image separation ( $R e_{2} = 2.07 \pm 0.02"$ ) of the outer ring (2) implies that it is at higher redshift. Its detection in the F814W filter implies zs2<6.9. The configuration can be well described by a total density profile $ρ_{t o t} r^{-} g^{'}$ with $g^{'} = 2.00 \pm 0.03$ and velocity dispersion $σ_{SIE}=287\pm5\kms$. [...] We consider whether this configuration can be used to constrain cosmological parameters exploiting angular distance ratios entering the lens equations. Constraints for SDSSJ0946+1006, are uninteresting due to the sub-optimal lens and source redshifts. We then consider the perturbing effect of the mass associated with Ring 1 building a double lens plane compound lens model. This introduces minor changes to the mass of the main lens and allows to estimate the mass of Ring 1 $(σ_{SIE,s1}=94\pm30\kms)$. We examine the prospects of doing cosmography with a sample of 50 double lenses, expected from future space based surveys such as DUNE or JDEM. Taking full account of the model uncertainties, such a sample could be used to measure $Ω_{m}$ and $w$ with 10% accuracy, for a flat cosmology.

The Sloan Lens ACS Survey. VI: Discovery and analysis of a double Einstein ring

Abstract

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