A CO observation of the Galactic methanol masers

Context We investigated the molecular gas associated with 6.7 GHz methanol masers throughout the Galaxy using a J = 1-0 transition of the CO isotopologues. Aims. The methanol maser at 6.7 GHz is an ideal tracer for young high mass star forming cores. Based CM molecular line emissions in the maser sources throughout the Galaxy, we can estimate their physical parameters and, thereby, investigate the forming conditions of the high-mass stars.