The overall distribution of carbon monoxide in the plane of the Galaxy

We observed the 2.6-mm line of CO at 5 deg longitude intervals along the galactic equator between 10 and 200 deg longitude with a velocity coverage sufficient to include all velocities expected in terms of differential galactic rotation. CO emission is generally observed at positive velocities (LSR) at less than 60 deg longitude up to the sub-central region terminal velocity. The spectra show considerable structure characterized by relatively small velocity dispersions of about 2 km/sec and antenna temperatures of 2 or 3 K. The characteristic appearance in the spectra of isolated features allowed us to make a rough estimate of the frequency of the occurrence of detected clumps of CO along the line of sight as 0.5/kpc. The observations show that 60 per cent of the CO emission observed originates between 4 and 8 kpc from the galactic center.