96 GHz emission was detected in all 12 observed sources. Fig. 1 shows the line spectra. The line parameters are presented in Table 2. Table 3 shows parameters of interest for the and lines determined by Slysh et al. (1996).
Table 2. Gaussian parameters of the lines detected at 96 GHz with their errors. The order of the lines: (upper), , and (lower)
Table 3. Gaussian parameters of thermal lines detected at 157 and 133 GHz. The data are taken from Slysh et al. (1996). Widths and radial velocities of the line are presented.
Comparison of the 96 and 157 GHz line parameters showed the following. The differences between line centre velocities at 157 and 96 GHz are much smaller than the linewidths. Thus, our results agree with the suggestion that the bulk of the emission at 157 and 96 GHz arises in a common region. Linewidths at 96 GHz are typically slightly smaller than those at 157 GHz. This is probably because the optical depths of the 96 GHz lines are smaller than those of the 157 GHz lines, as shown by statistical equilibrium calculations (see below).
The bottom row in Fig. 1 shows enlarged parts of NGC 2264, W 51Met3, and ON1 spectra with superimposed curves which represent the results of Gaussian fitting. These pictures show weak wings in the spectra of NGC 2264, W 51Met3, and possibly ON1. Similar wings are probably present in the spectra of DR 21(OH), W75N, Cep A, and S140. It is reasonable to suggest that these features dominate in the lines toward W 51Met3, W75N, and Cep A because these lines are approximately twice as broad as the other lines in the same sources. Broad wings were also detected in the line by Slysh et al. (1996) toward a number of sources. We could not fit these features by Gaussians due to their weakness and their blending with much stronger components. Further observations of these interesting features which are probably connected with high-velocity motions (bipolar outflows, cometary bow shocks of HII regions), are required.
© European Southern Observatory (ESO) 1997
Online publication: June 30, 1998