A Strong-Lens Survey in AEGIS: The Influence of Large-Scale Structure
Davis, Marc; Willmer, Christopher N. A.; Coil, Alison L.; Lotz, Jennifer M.; Fassnacht, Christopher D.; Koekemoer, Anton; Newman, Jeffrey A.; Guhathakurta, Puragra; Cooper, Michael C.; Moustakas, Leonidas A.; Hopkins, Andrew; Konidaris, Nicholas P.; Marshall, Phil
United States, Australia, Germany
Abstract
We report on a visual search for galaxy-scale strong gravitational lenses over 650 arcmin2 of HST ACS (V606 and I814) imaging in the DEEP2 Extended Groth Strip. This field has Keck DEIMOS spectroscopy of ~14,000 galaxies (~75% complete to RAB<24.1). We identify three strong galaxy-galaxy lenses: HST J141735+522646 is a previously known four-image lens (the ``Cross'' zl=0.8106, zs=3.40); HST J141820+523611 (the ``Dewdrop'' zl=0.5798, zs=0.9818) features two pairs of arcs; and HST J141833+524352 (the ``Anchor'' zl=0.4625, no zs) has one pair of arcs. Based on a normalized local density (1+δ3), lenses are found to be in both under- and overdense local environments. All three lenses are fit well by singular isothermal ellipsoid models including external shear, with χ2ν~1. The model shears are ~10%. Approximating all line-of-sight galaxies as singular isothermal sphere halos truncated at 200 h-1 kpc, with masses estimated through the Faber-Jackson relation, infers shears of ~2%, much smaller than those required by the models. Therefore, the corresponding convergence estimates must also be suspect. If more realistic treatment of galaxies (and the large-scale structure that they are embedded in) were to match the inferred shears to the model shears, then the true convergence could be measured and the mass-sheet degeneracy broken.