A CO survey of gravitationally lensed quasars with the IRAM interferometer

We present the results of a CO survey of gravitationally lensed quasars, conducted with the Plateau de Bure Interferometer over the last three years. Among the 18 objects surveyed, one was detected in CO line emission, while six were detected in the continuum at 3 mm and three in the continuum at 1 mm. The low CO detection rate may at least in part be due to uncertainties in the redshifts derived from quasar broad emission lines. The detected CO source, the z = 3.2 radio quiet quasar MG 0751+2716, is quite strong in the CO(4 3) line and in the millimeter/submillimeter continuum, the latter being emission from cool dust. The integrated CO line flux is 5.96 +/- 0.45 Jy.kms(-1), and the total molecular gas mass is estimated to be in the range M-H2 = 1.6-3.1 x 10(9) M-circle dot.