Cosmic Illusions: Strong Gravitational Lenses in the EGS

A careful visual search through the HST / ACS data revealed these spectacular galaxy-galaxy strong gravitational lenses. When a galaxy is sufficiently massive, and by good chance is in front of a much more distant galaxy, it can literally bend the light from the distant galaxy into highly magnified arcs, multiple image, or indeed into full "Einstein Rings." These EGS lenses sample the candy store, with the "Anchor" showing a skewed (but not surprising) paired-arc set of images(left), a near double-ring in the "Dewdrop" (center), and a classic "Einstein Cross" (right). With the three-dimensional map that our survey has built, we know what the large scale structure is along the lines of sight to these lenses, as traced by the galaxies we observe. The total influence of this matter ought to match up with what the gravitational lens models imply. Studying how these compare is only one of the many applications of this dramatic manifestation of geometry on cosmological scales.