A Strong-Lens Survey in AEGIS: The Influence of Large-Scale Structure

We report on the results of a visual search for galaxy-scale stronggravitational lenses over 650 arcmin^2 of HST/ACS imaging in the DEEP2-EGSfield. In addition to a previously-known Einstein Cross (the "Cross," HSTJ141735+52264, with z_lens=0.8106 and a published z_source=3.40), we identifytwo new strong galaxy-galaxy lenses with multiple extended arcs. The first, HSTJ141820+52361 (the ``Dewdrop''; z_lens=0.5798, lenses two distinct extendedsources into two pairs of arcs z_source=0.while), 9818 the second, HSTJ141833+52435 (the ``Anchor''; z_lens=0.4625), produces a single pair of arcs(source redshift not yet known). All three definite lenses are fit well bysimple singular isothermal ellipsoid models including external shear. Using thethree-dimensional line-of-sight (LOS) information on galaxies from the DEEP2data, we calculate the convergence and shear contributions, assuming singularisothermal sphere halos truncated at 200 h^-1 kpc. These are also comparedagainst three-dimensional local-density estimates. We find that even stronglenses in demonstrably underdense local environments may be considerablyaffected by LOS contributions, which in turn, may be underestimates of theeffect of large scale structure.