High-resolution observations of the W33 complex at 2.8, 6, 18 and 21 cm.

The H II-region complex W33 has been mapped in the continuum at three wavelengths: at 2.8 cm, 6 cm and 21 cm. The region consists of a number of weak discrete features and one strong component (G12.80 0.20). These features are superimposed on a broad background. The H109 alpha recombination line has been observed at four positions, and at three positions the profile has two components. The 6 cm H2CO line was also observed at three positions within W33, and at one position nearby. These data are consistent with either a chance superposition of two H II regions at different distance or with a single H II region with an expansion velocity near 13 km/s. The present observations, especially those of the H2CO absorption line, favour the first alternative. A new determination of the positions of the OH Type I emission sources W33A and W33B has been made with an accuracy of 2 sec.