We present observations of CO 1–0 and CO 2–1 emission from the z = 4.12 QSO PSS 2322+1944 using the Very Large Array .
The CO emission is extended on a spatial scale of 2 ^ { \prime \prime } .
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 the 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 } ) \sim 5 \times 10 ^ { 3 } cm ^ { -3 } ) , although such a conclusion is complicated by the possibility of differential gravitational magnification .