5 Conclusions

We present maps of the molecular emission towards nine IRAS sources, which in the WB89 catalogue had distinctly broad wings in their line profiles. Observations were done with the SEST, at the frequencies of ¹²CO(1-0), ¹³CO(1-0), C¹⁸O(1-0) and CS(2-1). From our ¹²CO(1-0) maps we conclude that seven of those sources (WB89 1099, 1135, 1173, 1181, 1187, 1189, 1275) are genuine outflow sources. One source (WB89 1275) shows a blue wing, but possible red wing emission is confused due to a close second velocity component. WB89 1086 shows no outflow emission at all. The remaining source (WB89 1262) was only observed in CS. The sources are all in or behind the region of the Vela Molecular Ridge (VMR), an active star-forming region, consisting of at least 4 GMC's with distances between 0.5 and 2-3 kpc. Based on the distances and the line velocities (Table 1), at most 6 of our sources are actually associated with the VMR; the remaining 3 lie at least 4 kpc further away.

The "pure'' outflow emission was found by first subtracting the contribution to the emission of non-associated components, using Gaussian fits. These additional emission lines were identified at positions away from the center of the flows. Then a correction was applied for the contribution of the emission of the quiescent gas to the wing emission (Sect. 3.1). Parameters of the outflow gas were then derived, assuming $T_{\rm {ex}}=20$ K and $\tau=1$ in all cases. All but two of the detected outflows are associated with IRAS sources located in the VMR (WB89 1135 and 1262 are more distant). The total (blue + red) velocity range of the flows is between 15.4 and 25.9 km$\,$s^-1. The outflows are barely resolved in the present observations: the spatial extent (0.22-2.65 pc) is about twice the beam size (in pc) in all sources. The mass contained in the flows lies between 1.1 $M_\odot$ (WB89 1099) and 150 $M_\odot$ (WB89 1135), which are (perhaps not surprisingly) the nearest and farthest objects where an outflow has been detected. Likewise, these two sources also determine the maximum range in energy ( $0.6-161\ 10^{44}$ erg). The dynamical timescale of all flows is of the order of 10⁵ years, typical for the age of Class I sources.

C¹⁸O(1-0) emission was observed and detected towards 7 out of 9 objects; CS(2-1) towards 8 out of 9. All spectra show single emission components, three of them show also line wings in CS emission. Single clumps are found in 5 sources, two sources have several clumps in one of the transitions (the other one not being mapped completely), and one source shows only weak emission. Masses range from 10 to 1000 $M_\odot$, radii from 0.2 to 2 pc. Radii determined from C¹⁸O and CS are similar. A velocity gradient (-2.0 to +1.9 km$\,$s^-1 pc^-1) is found in 5 sources.

Acknowledgements

This research was partly supported by the Deutsche Forschungsgemeinschaft through grant SFB-301. We thank C. Kramer and F. Massi for their comments on an earlier version of this paper. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.