Near-infrared and optical imaging of Q2345+007: The largest gravitationally lensed QSO system?

Abstract

We have taken K, R, V, and B band images of Q 2345+007, which has been claimed to be the gravitationally lensed quasar with the widest separation between the two images (approximately equal 7 arcsec), although the lens remains to be identified. The K band image extends the observations to longer wavelengths, and in conjunction with the published data and our new results at shorter wavelengths show that the colors of the two components do not differ markedly over the wavelength range 0.4-2.2 micrometers, though it is possible that the weaker component is slightly redder. From a comparison of our V and B band images with published images we find that the intensities of both components have declined substantially over the past decade. This opens up the possibility of testing the lensing hypothesis by measuring a temporal offset between the light curves of the two components.