A sensitive survey in 12CO J=1→0 of arm and interarm molecular clouds in the outer Galaxy

The effects of environment on the star formation process are currently not well understood. By studying the cloud populations in two different environments, spiral arms and the interarm regions, we hope to gain insight on the effects of environment in the star formation process. To this end, we are currently conducting a sensitive, 60‘ sampled survey of a one square degree region of the outer Galaxy in the J=1→0 transition of 12CO. Our survey region spans galactocentric radii between 9 and 16 kpc. Two populations of molecular clouds, arm and interarm, have been identified. The spiral arm population consists of GMC’s, with masses of 104 to 105 M⊙, and smaller clouds, clustered at velocities indicative of the 13 kpc spiral arm. The interarm clouds are dispersed throughout the remainder of the survey volume. The interarm population is comprised of small clouds with masses less than 104 M⊙.