Tootfinder

Locating Centers of Clusters of Galaxies with Quadruple Images: Witt's Hyperbola and a New Figure of Merit
Nixon Hanna, Paul L. Schechter, Michael A. McDonald, Marceau Limousin
https://arxiv.org/abs/2510.11356

Locating Centers of Clusters of Galaxies with Quadruple Images: Witt's Hyperbola and a New Figure of Merit
For any elliptical potential with an external parallel shear, Witt has proven that the gravitational center lies on a rectangular hyperbola derived from the image positions of a single quadruply lensed object. Moreover, it is predicted that for an isothermal elliptical potential the source position both lies on Witt's Hyperbola and coincides with the center of Wynne's Ellipse (fitted through the four images). Thus, by fitting Witt's Hyperbolae to several quartets of images - ten are known in Ab…