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Published online by Cambridge University Press: 25 May 2016
There is still debate as to whether wide separation (Δθ ≳ 3″) double quasars are physical binaries or gravitationally lensed sources. We proceed under the assumption that most of these objects are the result of lensing, and use maximum likelihood techniques (Kochanek 1993) to infer information about the mass distribution of deflectors that would be required to produce these wide image separations. Under the above assumptions, the most consistent explanation is the existence of a significant population of dark objects with the mass of groups of galaxies.