The quintuple quasar: Mass models and interpretation

The strange morphology of the six-component gravitational lens PMN J0134-0931 has resisted explanation. We present the first successful quantitative models for the system, based on the idea that there are two lens galaxies and two components of the background source. One source is quintuply imaged and corresponds to the five brightest observed radio components. The other source is triply imaged and corresponds to the sixth component, along with two others too faint to have been detected. The models reproduce the observed image positions and fluxes and make falsifiable predictions about other properties of the system. Some of these predictions have been confirmed by high-resolution radio and optical observations, as described in the companion paper by Winn and coworkers. Although we cannot determine the lens model uniquely with current data, we predict that the lens galaxies are spiral galaxies with roughly equal velocity dispersions σ ∼ 120 km s ^-1 and a projected separation of only 0″.4 (2 h^-1 kpc at z_l = 0.76). This system is the first known lens with five images of a single quasar and the second with more than four images.