A Catalog of CH 3 OH 7 0 –6 1 A + Maser Sources in Massive Star‐forming Regions

We present a Very Large Array survey of 44 massive star-forming regions in the 44 GHz 7 0 -6 1 A + methanol transition; 37 fields showed maser emission. Thirty-one sources were also observed in the 23 GHz 9 2 -10 1 A + methanol line; two fields showed maser emission. Although the 44 GHz line is a class I maser, we find a large number of these masers in relatively close association with H II regions and water masers. Several sources show strong evidence for a correlation between 44 GHz masers and shocked molecular gas, supporting the interpretation that molecular outflows may give rise to class I maser emission. We provide maser positions with arcsecond accuracy that not only locate the masers with respect to other star formation phenomena, but also provide, for the stronger masers, phase referencing sources that can be used to calibrate future 7 mm (44 GHz) observations of these regions.