The gravitational lensing nature of the Cloverleaf unveiled in CO (7-6) line emission.
Antonucci, R.; Tacconi, L.; Alloin, D.; Guilloteau, S.; Barvainis, R.
Abstract
We report 0.5" resolution imaging of the Cloverleaf quasar in the CO(7-6) line and 1.3mm 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 ~600pc for the CO emitting region. No continuum emission is detected: the measured flux density is 5 +/-3mJy, consistent with a spectral index larger than 3.