Distribution of H2CO absorption at 4.8 GHz towards M17

The complex consisting of the bright H II region M17 and its associated molecular cloud is known as a region of active star formation which contains an abundance of many different molecules. For H2CO, observations of a transition at 4.8 GHz towards the H II region show an intense narrow absorption feature with a radial velocity near +24 km/s superimposed on weak absorption which extends to below +10 km/s. The observations reported in connection with the present investigation were made with higher angular resolution and higher sensitivity than previously conducted studies. It is found that the H2CO distribution is in general similar to that observed by Lada and Chaisson (1975), although it differs in detail. Surprisingly, there is no evidence of an H2CO concentration near M17SW. It is belived that the interpretation of the absorption results in terms of cloud structure is severely limited by the location of some of the absorbing clouds behind the main M17 continuum.