The redshift of the lensing galaxy in the gravitationally lensed system B0218+35.7

Abstract

A spectrum of the light from the gravitationally lensed system B0218+35.7 has been obtained with the William Herschel Telescope. Narrow absorption and emission lines are detected with a redshift of 0.6847. We identify these lines as being produced in the lensing galaxy, which is probably a spiral. The light from the lensed object is red, with no strong emission lines.