A GALACTIC-CENTER SURVEY FOR 6.6-GHZ METHANOL MASERS

A new survey for 6.668-GHz methanol emission has been made over a 2-de g(2) area rewards the Galactic Centre. 23 maser sites can now be recog nized in the region, Most of them were known from previous searches, b ut the present observations with the Australia Telescope Compact Array allow many to be positioned to subarcsec accuracy for the first time. Preliminary results from a new hydroxyl 1665-MHz survey of the same r egion show that the masers of hydroxyl and methanol mostly coincide. T he methanol maser emission arises from the dusty Envelopes of newly fo rmed massive stars, and allows a census of these objects, unaffected b y obscuration from either around the star or along the line of sight. The space density of the maser sites at the Galactic Centre is found t o be similar to that in the spiral arms. implying that massive-star fo rmation is neither enhanced nor suppressed In the Galactic Centre at t he present lime. However, these statistics are heavily influenced by t he cluster of masers in the Sgr B2 complex which accounts for nearly h alf of the maser sites near tile Galactic Centre.