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We report the discovery of a new four-image gravitational lens in the radio source MG0751+2716.
Gravitational lensing occurs when the light from a distant source is deflected by the mass of an intervening lens. Since the gravitational deflection traces the total mass of the lens, gravitational lenses can be used to probe the dark matter distribution in galaxies. This approach can provide an important confirmation of dynamical mass profile determinations, and the lensing galaxies are typically at very great distances ($z\sim 1$).
MG0751+2716 was discovered as part of the MIT-Greenbank-VLA search for gravitational lenses (Hewitt 1986, Conner 1993, MIT Ph.D. theses), and consists of four compact radio components. High resolution MERLIN maps show an unresolved arc extending between the two brightest images. We present radio and optical observations of this system, and preliminary models of the lensing mass.