3 Results

During the survey 42 maser sources were detected out of 429 observed positions. Spectra of the sources are presented in Fig. 1, and the measured parameters are given in Table 1. Columns 1 - 3 are self-explanatory; Cols. 4 - 6 present the peak velocity, velocity range of the 6.7 GHz emission, and the flux density of the strongest feature, respectively. Columns 7-8 present near and far kinematic distance of the source. No measurable difference has been found between right and left polarizations. List of non-detections is in Table 2, given in electronic form; the typical detection limit for these sources is about 3 Jy. After completion of our observations papers by Walsh et al. (1995); van der Walt et al. (1995) and Lyder & Galt (1997) appeared where independent discovery of several 6.7 GHz masers is reported.

  

Table 1: Parameters of detected sources. BO, WC and HII in the last column mean that a source is associated with a bipolar outflow, an IRAS object that satisfy the WC colour criteria, or HII object from Helfand et al. (1992), respectively

Thirty-six masers were detected towards WC objects. In bipolar outflows nine masers were found, and all of them are associated with high-luminosity IRAS sources. Thus, the majority of the detections are associated with IRAS objects. However, not all of them satisfy the colour criteria by Wood & Churchwell. No masers were found in the vicinity of young stars of low and intermediate luminosity.

These cases are discussed in Sect. 4.

  

Figure 1: Spectra of sources, observed at 6.7 GHz. Spectra of sources 17436-2806, 17463-3128, 18151-1208, L379IRS2, 18316-0602, 18572+0057, 78.12+3.63 are shown with the velocity resolution 0.07 km s-1. For the rest of the sources the velocity resolution was 0.27 km s-1. Dashed lines indicate CS velocity of the parent molecular cloud

 

Figure 1: continued

 

Figure 1: continued

 

Figure 1: continued

 

Figure 1: continued

 

Figure 1: continued

3.1 Distances

The kinematic distances were obtained using the rotation curve by Brand & Blitz (1993)  

$$\frac\theta{\theta_0}=1.00767\left(\frac R{R_0}\right)^{0.0394}+0.00712$$ (1)

where $\theta$ is the linear velocity at the radius R, and $\theta_0=220$ km s^-1 is the linear velocities at the solar radius R₀=8.5 kpc.

We did not attempt to resolve the ambiguity in distance determination for several sources in which case we report both near and far solutions, although the near distances are more likely for a large number of observed sources. One can notice, that some sources have forbidden velocities and it's impossible to calculate their kinematic distances.