MOLECULAR CLOUDS IN THE EXTREME OUTER GALAXY

We present observations of 11 molecular clouds with kinematic Galactoc entric distances of 18-28 kpc. The most distant is similar to 10 kpc f arther from the Galactic center than any previously known and apparent ly lies beyond the edge of the optical disk. All are associated with m uch larger H I concentrations, with typical offsets of similar to 40 p c from the H I peaks. CO observations with the CfA 1.2 m and NRAO 12 m telescopes indicate typical sizes of 20-40 pc, velocity widths of 1-3 km s(-1), and kinetic temperatures of 10-25 K. They apparently have l ower CO luminosities than clouds near the solar circle with similar pr operties. Some may have associated infrared sources, but owing to the great distances of the clouds, the only general conclusion that can be made about star formation is that stars earlier than B1 are absent. T he apparent scarcity of clouds like these indicates that their contrib ution to the mass of the ISM beyond R = 18 kpc is not significant.