Is 3C324 the first gravitationally lensed giant galaxy?

Abstract

The radiogalaxy 3C324 has recently raised considerable interest as one of the most distant (redshift z = 1.206) and luminous known galaxies. Here we report new observations of this object at Canada–France–Hawaii Telescope which confirm our previous predictions of the presence of an intervening gravitational lens. First, a multiple structure is revealed by our charge-coupled device (CCD) broadband imagery. Second, following our previous identification in the 3C324 spectrum of an additional line system at z=0.84, subsequent CCD observation through interferential filters were planned. In a wavelength range corresponding to an emission line at z=0.84 only the central component is detected, while only outer components are seen in a range corresponding to a line redshifted by z=1.206. These observations are interpreted as the first example of gravitational multiple imaging of a giant radiogalaxy by a foregound object. So galaxy 3C324 seems to be a gravitational mirage—though further spectroscopic observations will be needed to establish whether the two images have similar spectra.