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Astron. Astrophys. 350, 659-671 (1999)


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Molecular outflows in intermediate-mass star forming regions: the case of CB3

C. Codella 1,2 and R. Bachiller 1

1 Observatorio Astronómico Nacional (IGN), Apartado 1143, 28800 Alcalá de Henares (Madrid), Spain
2 Istituto di Fisica dello Spazio Interplanetario, CNR, Area di Ricerca Tor Vergata, Via Fosso del Cavaliere, 00133 Roma, Italy

Received 8 June 1999 / Accepted 30 August 1999

Abstract

The intermediate-mass star forming region in the Bok globule CB3 has been investigated through a multiline survey at mm-wavelengths. We have detected a chemically rich bipolar outflow, driven by a probably Class 0 submillimetre source, which reveals different clumps along the main axis, indicating episodic increases of the mass loss process. The outflow is quite massive (4 [FORMULA]) and very powerful, since the kinetic energy is 5.5 1045 ergs and the mechanical luminosity is 5.6 [FORMULA]. The outflow motion is able to affect the structure of the globule and to clear a significant amount of the high-density gas hosting the star forming process. The dynamical flow parameters, as well as the analysis of the CO velocity profiles, place the CB3 outflow close to the HH7-11 and NGC2071 ones.

The CS maps reveal the molecular clump around the driving source, while the CS line profiles show a self-absorption feature consistent with the presence of infall motions. The CH3OH and SiO molecules are present only along the main outflow axis, confirming their close association with outflows, and their emission allows to detect the jet-like outflow structure and to point out four clumps with size less than 0.1 pc. We have detected two episodic mass losses, with ages of about 104 and 105 yr, indicating that the CB3 outflow is in a quite evolved evolutionary stage. Moreover, also the emission of S-bearing molecules such as SO, SO2, H2S and OCS is definitely enhanced towards the outflow. We have derived quite high densities, close to 105-106 cm-3, and the indication that SiO is tracing gas at higher density with respect to SO and CH3OH. The SiO molecule traces the highest velocity jet-like structure, while SO and CH3OH play an intermediate role between SiO and CO, being associated with more extended regions produced by interaction of the mass loss with the surrounding gas. We have found SO/H2S [FORMULA] SO2/H2S [FORMULA] 1, SO/SO2 [FORMULA] 1, OCS/H2S [FORMULA] 1 and SO/SiO [FORMULA] 1. These column density ratios, used as crude chemical clocks, indicate that the CB3 outflow in a relatively evolved evolutionary stage, in agreement with the age estimations based on its dynamics.

Key words: ISM: clouds – ISM: individual objects: CB3 – ISM: jets and outflows – ISM: molecules – radio lines: ISM

Present address: IFSI, CNR, Roma, Italy

Send offprint requests to: C. Codella (codella@ifsi.rm.cnr.it)

© European Southern Observatory (ESO) 1999

Online publication: October 4, 1999

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