GALACTIC METHANOL MASERS AT 6.6 GHZ

We have searched for 6.6-GHz methanol maser emission from the directio ns of more than 200 OH masers, together with a number of other sites o f star formation. We have also observed previously reported methanol m asers south of declination 24-degrees. Where we detected methanol emis sion, we measured its position and have found more than 40 instances o f small clusters of sources. We present observations of a total of 245 methanol masers with peak intensities ranging from 0.3 to 5000 Jy. Fo r a typical source, the velocity range of the emission is quite large - commonly 10 km s-1 and, in a few instances, exceeding 20 km s-1. Som e of the largest velocity ranges are suggestive of emission from an ou tflow region as well as a central source. Our observations over severa l epochs show that many sources possess at least some features whose i ntensity varies on a time-scale of several months. Towards most of the 6.6-GHz masers we have searched for 12-GHz methanol maser emission, a nd have made 131 detections; the median ratio of 12- to 6.6-GHz intens ity is 0.11. We discuss the general properties of this large sample of 6.6-GHz methanol masers. They appear to be more prevalent than OH mas ers, with intensities typically seven times higher, and are thus excel lent tracers of compact H II regions and sites of recent star formatio n.