Imaging low-order CO emission from the z = 4.12 quasi-stellar object PSS J2322+1944

We present observations of CO (1-0) and CO (2-1) emission from the z = 4.12 quasi-stellar object (QSO) PSS J2322+1944 using the Very Large Array.(1) The CO emission is extended on a spatial scale of 2". This extension could reflect the double nature of the QSO, as seen in the optical, or could be diffuse emission with a (redshift-corrected) mean brightness temperature of 2.8 K for the CO (2-1) line. We find that CO excitation conditions are lower than in two other IR-luminous z > 4 QSOs, suggesting the presence of a significant contribution from cooler, lower density molecular gas [n(H-2) similar to 5 x 10(3) cm(3), although such a conclusion is complicated by the possibility of differential gravitational magnification.