VLA observations of the 6 centimeter and 2 centimeter lines of H sub 2 CO in the direction of W49

Formaldehyde absorption at 6 cm and 2 cm toward the radio continuum source W49 has been mapped with the VLA, and Gaussian components have been fitted to the H{sub 2}CO profiles obtained in the direction of the embedded ultracompact H II regions. The densities of H{sub 2} and column densities of ortho-H{sub 2}CO are derived for the Gaussian range - 2 km/s and + 20 km/s. Large variations in optical depth are observed across the region. The structure and dynamics within the molecular core of W49 are determined. The main features of the results can be explained if the absorption occurs within the dense core of the molecular cloud and arises close to the embedded ultracompact H II regions UC H II. 57 refs.