Deep radio observation of the gravitational lens candidate QSO2345+007
Abstract
The double QSO2345+007 comprises two optical components separated by 7.1\ arcseconds and is the most prominent `dark matter' gravitational lens candidate. Despite being known for more than a decade, optical spectroscopy and imaging have been unable to determine whether this double QSO is a binary QSO or a gravitational lens system. In this note we report a deep VLA observation of this system, yielding a map with a noise level of 8.5 μJy per beam. We have a 4σ detection of a radio source within one arcsecond of the optical position of the brighter A-component of the QSO, but no significant detection of any radio counterpart of the B component. Given that the flux ratio in the optical waveband is 3--4, the gravitational lens hypothesis for this system would predict a radio flux of image B of 10 μJy. The non-detection of the B component is thus consistent with, but does not prove, the lens interpretation.
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