Lensed Image Angles: New Statistical Evidence for Substructure

Abstract

We introduce a novel statistical way of analyzing the projected mass distribution in galaxy lenses based solely on the angular distribution of images in quads around the lens center. The method requires the knowledge of the lens center location, but the images' distances from the lens center are not used at all. If the images of a quad are numbered in order of arrival time, θ_1 through θ_4, and θ_{ij} is the angle between images i and j, then we define the 'bisector' plane whose axes are linear combinations of θ_{23} and θ_{14}. The bisector plane of a given lens contains all the quads produced by the lens. We show empirically that all two-fold symmetric lenses with convex, i.e. non-wavy or petal-like isodensity contours are identical in the bisector plane of their quads. We also study lenses with twisting isodensity contours, lumpy substructure, etc. Our results suggest that to reproduce the general characteristics of the observed quad population, kpc-scale substructure must be a common feature of galaxy lenses.

30 pg, incl. 12 figs; accepted to ApJ; PDF with full resolution figures available at http://webusers.astro.umn.edu/~llrw/anglespaper.pdf

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• The impact of $\Lambda$CDM substructure and baryon-dark matter transition on the image positions of quad galaxy lenses
• The Fundamental Surface of Quad Lenses
• Model-free analysis of quadruply imaged gravitationally lensed systems and substructured galaxies
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• What Multiple Images Say About the Large-Scale Mass Maps of Galaxy Clusters