Astronomy and Astrophysics – Astrophysics
Scientific paper
Oct 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999a%26a...350..659c&link_type=abstract
Astronomy and Astrophysics, v.350, p.659-671 (1999)
Astronomy and Astrophysics
Astrophysics
29
Ism: Clouds, Ism: Individual Objects: Cb3, Ism: Jets And Outflows, Ism: Molecules, Radio Lines: Ism
Scientific paper
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 M_sun ) and very powerful, since the kinetic energy is 5.5 10(45) ergs and the mechanical luminosity is 5.6 L_sun . 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 CH_3OH 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 10(4) and 10(5) yr, indicating that the CB3 outflow is in a quite evolved evolutionary stage. Moreover, also the emission of S-bearing molecules such as SO, SO_2, H_2S and OCS is definitely enhanced towards the outflow. We have derived quite high densities, close to 10(5) -10(6) cm(-3) , and the indication that SiO is tracing gas at higher density with respect to SO and CH_3OH. The SiO molecule traces the highest velocity jet-like structure, while SO and CH_3OH 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/H_2S ~ SO_2/H_2S >= 1, SO/SO_2 =~ 1, OCS/H_2S >= 1 and SO/SiO >> 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.
Bachiller Rafael
Codella Claudio
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