1999A&A...350..659C

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 (4M_☉) and very powerful, since the kinetic energy is 5.5x10⁴⁵ergs and the mechanical luminosity is 5.6L_☉. 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 CB 3 outflow close to the HH 7-11 and NGC 2071 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 0.1pc. We have detected two episodic mass losses, with ages of about 10⁴ and 10⁵yr, indicating that the CB 3 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 10⁵-10⁶cm^–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∼SO₂/H₂S≥1, SO/SO₂≃1, OCS/H₂S≥1 and SO/SiO≫1. These column density ratios, used as crude chemical clocks, indicate that the CB 3 outflow in a relatively evolved evolutionary stage, in agreement with the age estimations based on its dynamics.