Astron. Astrophys. 347, 565-571 (1999)

5. Conclusions

We have carried out a survey of 3.15 in the Serpens star forming region with the Tautenburg Schmidt telescope in the [SII ]6716,6730 lines to search for outflows from young stars. We find a region of strong outflow activity centred on the Serpens Reflection Nebula (SRN), as well as two other outflows far away from the SRN. In a region of about 15´ (1.3 pc) diametre around the SRN, we discovered six new groups of HH objects in addition to the already known HH 106/107. Five groups of knots (HH 106/107, HH 460/HH 458, HH 478), together with several molecular hydrogen knots observed by other authors, we can assign to three independent outflows, and identify very likely exciting sources for them. For two more new groups of knots (HH 459, HH 455) from two other outflows we suggest more speculative exciting sources. Also for the two outflows far away from the SRN (HH 108/109, HH 476) no unique assignment of the source is possible so far.

Measuring the lengths of the HH flows in Serpens from their probable or potential sources, we find that with the exception of the parsec-scale flow HH 106/107 they all have lengths of 0.1-0.5 pc. Hence, their small kinematical ages of only 500 to 2500 years could hint at very recent star formation in Serpens. We suggest, however, that the flows are so short because they are rapidly breaking out of their dense parental clouds into very tenuous surroundings (as evidenced by the sharp edges of the dark clouds and filaments in Serpens), in which no further shock excitation of the terminal working surfaces of the flows can take place.

© European Southern Observatory (ESO) 1999

Online publication: June 30, 1999
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