The Gravitational Lensing Nature of the Cloverleaf Unveiled in CO (7-6) Line Emission

D.Alloin , S.Guilloteau , R.Barvainis , R.Antonucci , L.Tacconi
Service d'Astrophysique, CE Saclay, 91191 Gif-sur-Yvette Cedex, France
Institut de Radio Astronomie Millimétrique, 300 Rue de la Piscine, F-38406 Saint Martin d'Hères, France
MIT Haystack Observatory, Westford, MA 01886, USA
UC Santa Barbara, Physics Department, Santa Barbara, CA 93106 USA
Max Planck Institut fur extraterrestrische Physik, D-85748 Garching, Germany
Abstract: We report 0.5'' resolution imaging of the Cloverleaf quasar in the CO(7-6) line and 1.3 mm continuum,, as well as 1'' resolution imaging in the CO(3-2) line, performed with the IRAM interferometer. The CO(7-6) image is clearly resolved into 4 spots, demonstrating that the CO emission is also gravitationally lensed. We do not find any convincing evidence for a velocity gradient in the maps. As compared to the optical spots from a V band HST image, some of the CO spots are found to be stretched along the Einstein ring. Using the available lens model for the Cloverleaf, this suggests an intrinsic radius of  pc for the CO emitting region. No continuum emission is detected: the measured flux density is  mJy, consistent with a spectral index larger than 3.