2000A&A...354..236E

Deep imaging in the 1-0 S(1) line of molecular hydrogen was used to search for parsec-scale molecular outflows in L 1448, NGC 2071, and NGC 7129. Apart from seven parsec-scale flows, 21 other, shorter molecular outflows were found. This means that on average 25% of the molecular flows are of parsec-scale length, with a variation from 17 to 50% in the three observed regions. For the 28 outflows, only eight driving sources could be identified with near-infrared sources or nebulosity in our images. Six further sources likely are known deeply embedded Class0 objects, while for 14 flows no sources could be identified. Therefore, these objects presumably are also deeply embedded, and are good Class0 candidates. We find no evidence for different absolute lengths of the parsec-scale molecular flows from known Class0 and ClassI sources in the observed regions, i.e. the length of these flows is not indicative of their true age. These flows have broken out of their cloud cores and likely are moving through a medium too tenuous to produce further visible shock emission. Moreover, even for the flows from the Class0 sources we derive kinematical ages of up to 2x10⁴ years, comparable to the lifetime of these sources, and indicating that outflow activity must start very early in the Class0 phase of star formation, or even before. Four molecular H₂ outflows with a high degree of curvature are found in our sample, and mechanisms for their bending are discussed.