Abstract
VLA maps of W31, W33, W49, W51 in the 6-cm line of ortho-formaldehyde are presented. The maps were made with angular resolutions of 10-15 arcsec and a velocity resolution of 1.8 km/s. The total velocity coverage was 45 km/s. In all of the regions measured, the ortho-H2CO distribution breaks up into a number of condensations or clumps. For W33 and W49, all of the single-dish line flux density is present in the VLA maps; for the other two, about 70 percent is measured. Detailed discussions of the maps of the individual regions are presented, and conclusions based on the observations are given. (D.H.)