DETECTION OF WIDESPREAD STRONG METHANOL MASERS AT 44 GHZ

The Haystack Observatory 37 m antenna was used to search for emission from the 44 GHz 70 → 61 A+ transition of interstellar methanol toward 50 galactic star-forming regions. The line was detected toward half the observed sources. Several of these regions were also observed in the 36 GHz 4-1 → 30 E line. In most sources, the detected emission shows one or more narrow components indicating maser action. The spectral appearance and spatial distribution of these methanol masers closely resembles the properties of the well-studied 25 GHz methanol masers: in some cases, distances between individual methanol maser components are of order 1 pc. Unlike the now well-studied 12 GHz methanol masers, these masers appear well separated from OH/H2O maser centers and compact H II regions.