2002A&A...383..502K

We present near-infrared and millimetre observations of the large Bok globule CB34. Two long parallel trails of H₂ knots are discovered on wide-field images in the 1-0 S(1) 2.12µm emission line. These parsec scale H₂ jets extend to the edge of the dark globule where they disappear without the trace of bow shocks. This suggests that the outflows physically extend into a lower density ambient medium where their terminating bows are beyond present detection limits. The two outflows are extremely well collimated and parallel to within 3°. The outflow mechanical luminosity, derived from CO measurements, and the shocked luminosity, estimated from the H₂ emission, are similar, consistent with jet-driven non-evolving outflow structure. The jets appear to originate from the densest cores, as observed in H¹³CO⁺ line emission. A central concentration of reddened stars and a lower density halo of less reddened stars within the globule are revealed by JHK photometry. Disordered motions are observed in the CO J=2-1 line velocity channel maps and can be driven by the power of the outflows emanating from dense cores. We sketch a picture for the star formation history of the globule in which two star phases have been formed. A weak diffuse emission halo is detected in the near infrared with colours consistent with either scattered light or a ro-vibrational H₂ cascade. We propose that the halo is produced by ongoing H₂ formation. Cloud evolution and halo H₂ formation timescales are then both a few x10⁵yr. Thus, we may be witnessing the formation of a molecular cloud out of diffuse atomic gas. This supports a scheme in which this Bok globule has formed independently rather than through dislocation from a nearby molecular cloud.