MOLECULAR SPIRAL ARMS IN M31

We describe a high-resolution, high-sensitivity CO(1-0) survey of a la rge fraction of the south-west star-forming ''ring'' 20 kpc in diamete r in M31 made with the 14 m FCRAO telescope and its QUARRY receiver ar ray. At the 45 '' angular resolution of the telescope, the ring is res olved into giant complexes of molecular gas with typical sizes of a fe w hundred parsecs and masses in excess to 10(6) M.. Most of these deli neate a prominent spiral arm coincident with that traced by atomic hyd rogen and dust. This arm appears in all respects quite similar to a pr ominent spiral arm in our Galaxy at about the same Galactic radius: th e Carina arm. Closer to the center, a second fainter molecular spiral arm segment with an H I and dust counterpart is also detected. The mai n OB associations and the UV light define an arm offset from that trac ed by the gas by about 500 pc. The H II regions are mainly found eithe r along the edge of the prominent gaseous arm which faces the associat ions, or aligned with the second fainter gaseous arm. They define Baad e's arms S4 and S3, respectively.