Synthesis images of 6.7 GHz methanol masers

Abstract

We have used the Australia Telescope Compact Array to produce maps in the 6.7 GHz (5(1)-6(0)A(+)) transition of a number of methanol masers associated with star-forming regions and compared them with earlier maps of the 12.2 GHz (2(0)-3(-1)E) methanol masers. We find that in several cases the 6.7 GHz and 12.2 GHz maser positions are coincident to within our positional accuracy of 0.02 arcsec, placing a tight constraint on pumping mechanisms. We also find that the methanol masers are frequently located along lines or arcs, sometimes with velocity gradients along them, and interpret this to indicate the existence of edge-on protoplanetary disks around the nascent stars.