A galactic centre survey for 6.6-GHz methanol masers

A new survey for 6.668-GHz methanol emission has been made over a 2-deg(2) area rewards the Galactic Centre. 23 maser sites can now be recognized in the region, Most of them were known from previous searches, but 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 region show that the masers of hydroxyl and methanol mostly coincide. The methanol maser emission arises from the dusty Envelopes of newly formed massive stars, and allows a census of these objects, unaffected by 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 to be similar to that in the spiral arms. implying that massive-star formation is neither enhanced nor suppressed In the Galactic Centre at the present lime. However, these statistics are heavily influenced by the cluster of masers in the Sgr B2 complex which accounts for nearly half of the maser sites near the Galactic Centre.