A CS STUDY OF STAR-FORMING REGIONS PREVIOUSLY MAPPED IN AMMONIA

We have mapped the CS (J = 1 --> 0) emission in six star-forming regions using the 14 m telescope of the Centro Astronomico de Yebes: L1524 (Haro 6-10), AFGL 5142, AFGL 5157, NGC 2068 (HH 19-27), L43 (RNO 91), and HHL 73. These sources have been previously mapped with similar resolution in the (J, K) = (1, 1) inversion transition of NH3. In general, the CS emission has been found to be more extended than the NH3 emission, the maximum size ratio being approximately 5, for the L1524 region. We have found displacements in the position of the peaks of the CS and NH3 maps of the order of 0.1 pc. In all the sources these peaks lie very close to IRAS point sources. In particular, in the HHL 73 region we have found three main CS condensations, each one associated with an IRAS source, and with an NH3 clump. We have found that the CS lines are broader than the NH3 lines, and that the CS line width increases with the size of the CS condensation, following a power law of index alpha congruent-to 0.5. We have measured velocity gradients of approximately 0.5 km s-1 pc-1 in almost all the regions, compatible with gravitationally bound motions. We have also observed with the IRAM 30 m telescope the CO (J = 2 --> 1), (CO)-C-13 (J = 1 --> 0), and (CO)-O-18 (J = 1 --> 0) rotational transitions towards the L43 region. We have detected small systematic shifts in the line center velocities of these isotopes, compatible with an expansion motion of the outer part of the ambient cloud.