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Astron. Astrophys. 354, 236-246 (2000)


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Parsec-scale molecular H2 outflows from young stars

Jochen Eislöffel *

Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany

Received 13 September 1999 / Accepted 2 December 1999

Abstract

Deep imaging in the 1-0 S(1) line of molecular hydrogen was used to search for parsec-scale molecular outflows in L1448, 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 Class 0 objects, while for 14 flows no sources could be identified. Therefore, these objects presumably are also deeply embedded, and are good Class 0 candidates.

We find no evidence for different absolute lengths of the parsec-scale molecular flows from known Class 0 and Class I 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 Class 0 sources we derive kinematical ages of up to 2[FORMULA]104 years, comparable to the lifetime of these sources, and indicating that outflow activity must start very early in the Class 0 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.

Key words: shock waves – molecular processes – stars: formation – ISM: jets and outflows

* Visiting Astronomer, German-Spanish Astronomical Centre, Calar Alto, operated by the Max-Planck-Institute for Astronomy, Heidelberg, jointly with the Spanish National Commission for Astronomy.

Send offprint requests to: Jochen Eislöffel (jochen@tls-tautenburg.de)

© European Southern Observatory (ESO) 2000

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