Comparative Analysis of Molecular Clouds in M31, M33, and the Milky Way

We present BIMA observations of a 2′ field in the northeastern spiral arm of M31. In this region we find six giant molecular clouds (GMCs) that have a mean diameter of 57 ± 13 pc, a mean velocity width of 6.5 ± 1.2 km s−1, and a mean molecular mass of (3.0 ± 1.6) × 105 M☉. The peak brightness temperature of these clouds ranges from 1.6 to 4.2 K. We compare these clouds to clouds in M33 observed by Wilson & Scoville using the OVRO millimeter …