3 Results

Observations of 158 sources were successfully carried out (111 bipolar outflows, 26 Class I methanol masers, and 47 Class II methanol masers - some objects are methanol masers of Class I and II simultaneously or bipolar outflow and methanol masers). Of the 158 sources, 149 were detected in the CS(2-1) line (97 bipolar outflows, 26 Class I methanol masers, 45 Class II methanol masers). Of these 149 sources, 51 were observed in the C³⁴S line. The list of bipolar outflows was compiled from the catalogues of Fukui (1989) and Xiang & Turner (1995). The list of Class I methanol masers was compiled from the following surveys: Haschick et al. (1990), Bachiller et al. (1990), Kalenskii et al. (1992), Kalenskii et al. (1994). The list of Class II methanol masers was compiled from the surveys of Menten (1991) and Slysh et al. (1998).

At the present time 27 strong Class I methanol masers with a flux $\ge$ 50 Jy at 44 GHz are known. It is possible to observe 14 of them at Onsala. Some well known masers were left out of our survey, such as Ori KL, OMC-2, and DR21(OH), but some were included for comparison. Of the remaining 11, only 7 were observed, because of weather conditions. The other 19 Class I methanol masers of our list have a lower flux at 44 GHz. We will call a CS line with an integrated intensity > 10 K km s^-1, i.e. $\approx$ 200 Jy km s^-1, "strong''. Of 7 strong Class I methanol masers (S235B, G30.80-0.10, W51 e1/e2, W75N, DR21-West, W33-Met, L379IRS3) only one (G30.80-0.10) has a weak CS line (integrated intensity less than 10 K km s^-1). The others are stronger.

Class II methanol masers, on average, are more powerful than Class I methanol masers. Twenty-seven Class II methanol masers, detected by Menten (1991), have a flux higher than 100 Jy. It is possible to observe 21 sources of this list at Onsala. Eleven sources were observed in our survey and 6 out of them (S231, S252, G9.62+0.19, W33B, W51, W75 N) exhibit a strong CS line.

All observational data were reduced with the CLASS software package (Groupe d'Astrophysique de Grenoble). The results of the observations are presented in Table 1. Columns 1, 2, and 3 give the source name, R.A. and Dec., respectively; Col. 4 gives the number of components and type of lines (components of the C³⁴S line are marked by a star), and Cols. 5-8 give the Gaussian fitting parameters. In the last column the sources are marked BO - bipolar outflow, MMI - Class I methanol maser, MMII - Class II methanol maser. The list of sources with negative results (emission with $T_{\rm A}^*<$ 0.03 K) is presented in Table 2. For the positive results the CS(2-1) line was detected in 93% of the bipolar outflows, in 100% of the Class I methanol masers and in 96% of the Class II methanol masers. All sources observed in the C³⁴S line gave a positive result.

Spectra of sources detected in the CS line only are shown in Fig. i, and spectra of sources detected in both the CS and C³⁴S lines are shown in Fig. ii (these figures are shown in the online version of the paper only).

A complex line shape was observed in 40% of the sources - one can approximate it as a sum of two Gaussians, a strong narrow and weak broader line. In these cases the parameters of both lines are given in Table 1. The shape of the lines is often asymmetrical and looks like a right or a left wing of the central component.

 

Table 2: Sources without detected emission in the CS(2-1) line